Less Favourable Treatment of Part-Time Workers

Part-time working is a well-established feature of the UK labour market, offering flexibility for both employers and workers. However, employing part-time staff carries specific legal responsibilities, particularly around ensuring they are not treated less favourably than comparable full-time workers. Failures in this area can expose employers to employment tribunal claims, reputational risk and avoidable management disputes.

Less favourable treatment issues most commonly arise where part-time workers receive different pay structures, reduced access to benefits, fewer opportunities for training or progression, or less generous holiday arrangements. In many cases, these differences are applied unintentionally, often as a result of legacy policies or assumptions about working hours. UK employment law places a clear obligation on employers to actively assess whether such differences are lawful and objectively justified.

For HR professionals and business owners, understanding how the law defines less favourable treatment, and how the comparator framework operates in practice, is essential to maintaining compliant and fair working arrangements. This is particularly important in organisations with mixed workforces where full-time and part-time roles operate side by side.

What this article is about

This article provides a comprehensive overview of the concept of less favourable treatment as it applies to part-time workers under UK employment law. It explains how the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000 operate, the central role of the comparable full-time worker test and the circumstances in which different treatment may, or may not, be lawful.

The guide is written for HR professionals and business owners and focuses on practical compliance. It examines common risk areas, explains how employers can objectively justify different treatment where appropriate and outlines the potential consequences of getting this wrong. The aim is to help employers identify, prevent and manage less favourable treatment issues within their workforce. The protections under the Regulations apply to both employees and workers, so employers should assess risk across their whole workforce, not only those with employee status.

Section A: What Is Less Favourable Treatment in Employment Law

Less favourable treatment is a specific legal concept used in UK employment law to describe situations where a worker is treated worse than another worker in comparable circumstances, without lawful justification. In the context of part-time workers, the concept is primarily governed by the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000, which were introduced to prevent discrimination based solely on an individual’s part-time status.

Under the Regulations, a part-time worker has the right not to be treated less favourably than a comparable full-time worker as regards the terms of their contract or by being subjected to any other detriment. This protection is primarily set out in Regulation 5, and it applies where the reason for the less favourable treatment is that the worker is employed on a part-time basis. The protection covers both contractual terms and wider workplace treatment, and it is not limited to written contractual provisions. It is not necessary for the employer to intend to discriminate; unintentional or indirect differences in treatment can still amount to a breach.

Less favourable treatment can arise in a wide range of employment contexts. It may relate to pay, contractual benefits, access to training, opportunities for promotion, working patterns, or the application of workplace policies. Importantly, the comparison is not with full-time workers generally, but with a specific comparable full-time worker who meets the statutory criteria. This means that employers must assess treatment on a role-by-role basis rather than relying on broad workforce practices.

The Regulations do not prohibit all differences in treatment between part-time and full-time workers. The legal focus is on whether the treatment is less favourable and whether the reason for that treatment is the worker’s part-time status. Where a difference in treatment exists, the employer must be able to demonstrate that it is objectively justified. If the employer cannot do so, the treatment is likely to be unlawful.

For employers, the key compliance challenge is recognising that less favourable treatment is not limited to obvious disparities such as lower hourly pay. More subtle practices, such as excluding part-time staff from discretionary benefits or structuring roles in ways that limit access to progression, can also fall within the scope of the Regulations if they disadvantage part-time workers because of their working hours.

Section summary

Less favourable treatment occurs where a part-time worker is treated worse than a comparable full-time worker because of their part-time status. The concept is defined by the Part-time Workers Regulations and applies broadly to contractual terms and workplace treatment, including being subjected to any other detriment. Employers must identify any differences in treatment and be able to justify them objectively at the point the treatment occurs, or risk breaching employment law.

Section B: The Comparable Full-Time Worker Test

The concept of less favourable treatment cannot be assessed in isolation. Under the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000, a part-time worker’s treatment must be compared against that of a specific comparator. This is known as the comparable full-time worker test and it sits at the centre of any legal analysis under the Regulations.

A comparable full-time worker is someone who is employed by the same employer, works under the same type of contract and is engaged in the same or broadly similar work as the part-time worker. In assessing whether work is the same or broadly similar, the law requires consideration of factors such as skills, qualifications and experience, rather than simply job titles. Minor differences in duties will not prevent a comparison if, overall, the roles are substantially similar.

The requirement that the comparator be employed by the same employer is important. Comparisons cannot be made with workers employed by a different legal entity, even if they work within the same group or at the same site. In addition, agency workers cannot act as comparators for the purposes of the Part-time Workers Regulations, as they are not employed by the end user under the same contractual framework.

Where there is no actual full-time worker carrying out the same or broadly similar role, the Regulations allow for a hypothetical comparator to be used. This means the employer must consider how a full-time worker would be treated if one were employed in that role. Employers cannot avoid compliance simply because their workforce consists entirely of part-time staff or because a role is structured to be part-time only.

The comparator test focuses on treatment rather than outcomes alone. For example, differences in total pay may be lawful where they reflect fewer working hours, but differences in hourly rates or access to benefits may amount to less favourable treatment if they cannot be objectively justified. Employers must therefore ensure that any comparison is carried out on a pro rata basis where appropriate.

From a practical perspective, the comparable full-time worker test requires employers to understand their workforce structures and contractual arrangements in detail. HR policies and reward frameworks should be designed with this comparison in mind, ensuring that part-time workers are not disadvantaged simply because of their working pattern.

Section summary

The comparable full-time worker test is the foundation of less favourable treatment analysis. Employers must compare part-time workers with a suitable full-time comparator doing the same or broadly similar work under the same type of contract. Where no actual comparator exists, a hypothetical one may be used. Proper application of this test is essential to assessing whether treatment is lawful.

Section C: Common Examples of Less Favourable Treatment

In practice, claims of less favourable treatment often arise from everyday employment decisions rather than deliberate attempts to disadvantage part-time staff. Many issues stem from standard policies or historical practices that have not been reviewed through the lens of part-time worker protections. For employers, understanding where risk commonly arises is critical to maintaining compliance.

One of the most frequent areas of concern is pay. While it is lawful for part-time workers to receive less total pay than full-time workers because they work fewer hours, problems arise where the hourly rate of pay is lower, or where part-time workers are excluded from pay enhancements, overtime rates or performance-related bonuses without objective justification. Exclusion from overtime opportunities can amount to less favourable treatment even where overtime is discretionary, if access is limited because of part-time status rather than operational need.

Holiday entitlement is another common risk area. Part-time workers are entitled to the same statutory holiday entitlement as full-time workers, calculated proportionately according to hours or days worked. Less favourable treatment may occur where part-time workers receive fewer bank holidays than they are entitled to on a pro rata basis, or where holiday policies are structured in a way that disproportionately disadvantages those who do not work standard full-time patterns.

Access to pensions and other benefits can also give rise to less favourable treatment. Excluding part-time workers from occupational pension schemes, enhanced sick pay, enhanced redundancy pay, private medical insurance or other benefits, or imposing more restrictive eligibility criteria, may be unlawful unless the employer can demonstrate objective justification. Cost considerations alone are unlikely to be sufficient justification.

Training, development and promotion opportunities present a further area of risk. Part-time workers must not be overlooked for training, appraisals or progression because of assumptions about availability or commitment. Decisions that indirectly disadvantage part-time workers, such as scheduling mandatory training on non-working days without alternative options, may amount to less favourable treatment.

Less favourable treatment can also arise in more subtle ways, including reduced access to workplace facilities, less favourable shift allocation, or exclusion from workplace communications and meetings. Even where the impact appears minor, the cumulative effect of such practices can support a claim if they are linked to part-time status.

Section summary

Common examples of less favourable treatment include lower hourly pay, restricted access to overtime, reduced access to benefits such as enhanced sick pay or redundancy pay, disadvantageous holiday arrangements and limited training or progression opportunities. Employers should review policies and practices carefully to ensure part-time workers are treated fairly on a pro rata basis and are not disadvantaged because of their working hours.

Section D: When Different Treatment May Be Lawful

The Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000 do not require employers to treat part-time and full-time workers identically in all circumstances. Instead, the law recognises that there may be situations where different treatment is justified, provided the employer can demonstrate that it is objectively justified.

Objective justification requires the employer to show that the less favourable treatment pursues a legitimate business aim and that the means of achieving that aim are appropriate and necessary. This is a two-stage test. First, the employer must identify a genuine and lawful objective that is unrelated to the individual’s part-time status. Secondly, the employer must show that the treatment is proportionate, meaning there is no less discriminatory way of achieving the same aim.

Legitimate business aims may include factors such as ensuring business efficiency, maintaining service quality, or addressing genuine operational requirements. While financial considerations may form part of the justification, cost alone is unlikely to be sufficient. Tribunals will examine closely whether the employer has explored alternative, less discriminatory options and whether the impact on part-time workers is justified.

The burden of proof rests with the employer. If a part-time worker establishes that they have been treated less favourably than a comparable full-time worker because of their part-time status, the employer must provide clear evidence of objective justification. This includes demonstrating how the decision was reached and why less disadvantageous measures were not adopted. Importantly, justification is assessed at the time the treatment occurs, not retrospectively after a complaint has been raised.

Employers should also be aware that justification must be assessed on a case-by-case basis. A justification that applies in one role or department may not apply in another. Regular review of policies and decisions is therefore essential, particularly where working patterns or business needs change over time.

From a practical HR perspective, employers should document the reasoning behind any differential treatment of part-time workers and ensure decision-makers understand the legal threshold for objective justification. This proactive approach can significantly reduce the risk of disputes and tribunal claims.

Section summary

Different treatment of part-time workers may be lawful where the employer can objectively justify it. This requires a legitimate business aim unrelated to part-time status and proportionate means assessed at the time the treatment occurs. The burden of proof lies with the employer, and cost alone is rarely sufficient. Careful assessment and documentation are essential to manage risk.

FAQs

What counts as less favourable treatment for part-time workers?
Less favourable treatment occurs where a part-time worker is treated worse than a comparable full-time worker because they work part time. This can relate to contractual terms such as pay, holidays and benefits, or to wider workplace treatment such as access to training, promotion or facilities. The key question is whether the difference in treatment is linked to part-time status and cannot be objectively justified.

Do part-time workers always have to be treated the same as full-time workers?
No. The law does not require identical treatment in all circumstances. Differences that reflect fewer working hours, such as lower total pay or fewer working days, are usually lawful if applied on a pro rata basis. However, where treatment is genuinely less favourable, the employer must be able to objectively justify it.

Can pay be calculated differently for part-time workers?
Employers can lawfully pay part-time workers less in total because they work fewer hours, but the hourly rate should generally be the same as that of a comparable full-time worker. Excluding part-time workers from bonuses, overtime rates or pay enhancements may amount to less favourable treatment unless objectively justified.

What if there is no comparable full-time worker?
If there is no actual full-time worker carrying out the same or broadly similar role, the law allows for a hypothetical comparator. Employers must consider how a full-time worker in that role would be treated and assess whether the part-time worker is disadvantaged in comparison.

Does length of service justify different treatment?
Length of service may justify different treatment if it can be objectively justified and pursues a legitimate business aim. However, service-based thresholds that automatically exclude part-time workers may still amount to less favourable treatment if they disproportionately disadvantage part-time staff and cannot be justified.

Can less favourable treatment lead to tribunal claims?
Yes. Part-time workers can bring claims in the employment tribunal if they believe they have been treated less favourably in breach of the Regulations. Employers may be liable even where they believed treatment was fair or consistent with industry practice.

Conclusion

Less favourable treatment of part-time workers is a significant and often underestimated area of employment law risk for UK employers. The Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000 impose clear obligations to ensure that workers are not disadvantaged simply because they work fewer hours than their full-time colleagues.

For HR professionals and business owners, compliance depends on understanding how the comparable full-time worker test operates in practice and recognising that less favourable treatment can arise in many aspects of the employment relationship. Pay structures, holiday arrangements, access to benefits and opportunities for progression all require careful consideration and, where appropriate, pro rata treatment.

Where differences in treatment exist, employers must be able to demonstrate objective justification supported by evidence and sound reasoning. Liability can arise even where the employer believed treatment was fair, reasonable or consistent with common practice. The burden of proof rests with the employer, and justification must be assessed at the time the treatment occurs.

Regular policy reviews, consistent decision-making and clear documentation are essential tools in managing this risk. By taking a proactive approach to part-time worker treatment, employers can reduce the likelihood of disputes, support fair and inclusive working practices and ensure compliance with UK employment law.

Glossary

Useful Links