Applying the same requirements to part-time and full-time staff may not always be lawful following a recent Supreme Court decision. We explain the decision and its implications for employers.

Published: 9 September 2026
Authors: Phil Crowe

In Augustine v Data Cars Ltd, the Supreme Court has confirmed the scope of the protection provided by the Part Time Workers (Prevention of Less Favourable Treatment) Regulations 2000 (PTWR).

Regulation 5(2) of the PTWR provides that part-time workers are protected from being treated less favourably by their employer than comparable full-time workers, where:

(a)    the treatment is on the ground that the worker is a part-time worker

(b)    the treatment is not objectively justified.

The Supreme Court considered what “on the ground” meant and clarified that part-time workers need only demonstrate that their part-time status was an effective cause of the less favourable treatment. There is no requirement for the part-time status to be the sole cause of the less favourable treatment for a claim to succeed.

Background

Mr Augustine worked as a part-time driver for Data Cars, working an average of 34.8 hours per week. All drivers were required to pay a fixed weekly fee of £148 to access the company's booking dispatch system, regardless of the number of hours they worked. Mr Augustine argued that this amounted to less favourable treatment because part-time drivers effectively paid a higher fee per hour worked than comparable full-time drivers.

The Employment Tribunal disagreed with Mr Augustine, finding that the Respondent’s application of the fixed weekly fee would only amount to less favourable treatment if it was charged on the ‘sole ground’ that Mr Augustine was a part-time driver, and this was not the case.

On appeal the EAT and Court of Appeal agreed that Mr Augustine had been subjected to less favourable treatment. However, they considered themselves bound by the earlier decision in McMenemy v Capita Business Services Ltd, which held that part-time status had to be the sole cause of the treatment complained of. Mr Augustine appealed to the Supreme Court to determine whether part-time status needed to be the sole cause of the less favourable treatment, or merely an effective cause.

Supreme Court decision

The Supreme Court unanimously allowed the appeal. The Court held that a worker will be protected by Regulation 5(2) if they can establish that their part-time status was an effective cause of the less favourable treatment. The Court pointed out that the language in Regulation 5(2) deliberately mirrored the language used in other pre-existing discrimination legislation, and in those areas an effective cause test had also been applied.

What does this mean for employers?

The bar for part-time workers to be protected from less favourable treatment is now much lower due to the legal test being clarified in this decision. As such, it will be much easier for part-time workers to establish that they have been treated less favourably by their employer. The decision is likely to encourage greater scrutiny of practices affecting part-time workers and may increase the scope for workers to bring successful claims under the PTWR.

The decision is particularly significant because employers can no longer defend claims simply by pointing to another reason for the treatment in question. Prior to Augustine, employers could often rely on the argument that a measure was adopted for a broader commercial or operational reason and was not imposed solely because an individual worked part-time. Following the Supreme Court's judgment, this will not necessarily be enough. If part-time status is found to have been a material or effective contributing factor to the disadvantage suffered, the protection under the PTWR may apply. Employers should therefore carefully assess whether part-time workers are being adversely affected by workplace policies and/or practices, even where those are driven by legitimate business considerations.

What steps should employers take now?

To reduce the likelihood of disputes arising from part-time workers, we recommend that employers review all policies and practices and identify any which apply uniformly to part-time and full-time workers. This may include practices such as chargeable fixed fees (as in Augustine), minimum sales or productivity requirements, criteria for bonus schemes, training commitments, or attendance requirements. At first glance, it may seem that a policy or practice is being applied equally to all workers and so deemed to be fair. However, if the practical effect is that part-time workers will bear a greater disadvantage than comparable full-time workers, then one option is for employers to amend these policies and practices to reduce any less favourable treatment being suffered by part-time workers.

It may also be possible for an employer to objectively justify a policy which disadvantages part-time workers, on the basis that it is a proportionate means of achieving a legitimate business aim. However, given that the part-time status now need only be an effective cause of the less favourable treatment, a Tribunal is more likely to scrutinise the employer’s reasons for the treatment, meaning it will likely be more difficult for employers to defend claims on the basis of objective justification going forwards. Employers should maintain a clear record of their business decisions and reasons for maintaining any policies or practices that disadvantage part-time workers. Should a part-time worker bring a claim in the future, then these records will be key when considering any objective justification defence.

Conclusion

The key message from Augustine is that employers can no longer assume a claim can be successfully defended where there are multiple reasons for the treatment complained of by the part-time worker. If part-time status is an effective cause of a disadvantage, the part-time worker is likely to be protected from less favourable treatment by the PTWR, unless the practice can be objectively justified. Employers should therefore focus on identifying practices that may adversely affect part-time workers and ensure these can be objectively justified rather than relying on alternative explanations for these practices.