It is unlawful to treat a worker less favourably because of their status as part-time, as set out by the Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000 (‘2000 Regulations’). The above case looked at the test for causation under this legislation and clarified what the correct factors for consideration were.

Mr Mireku had had his claim rejected by the Employment Tribunal, for less favourable treatment, contrary to the 2000 Regulations. This related to the cancellation of overtime – the Tribunal found that this had been cancelled for reasons that were unconnected to him being part-time. Mr Mireku’s subsequent appeal centred on the Tribunal applying the wrong causation test.

There had until this point been conflict in the authorities re. the causation test. In summary, one previous case had found that part-time status must be the sole reason for less favourable treatment whilst another suggested the status need only be an ‘effective and predominant cause’ of the treatment.

However, an earlier case, post-dating both of the above, analysed the conflicting authorities and found that whilst it may not have been the most preferable option, the court was bound by the ‘sole reason’ test.

Therefore, in the Mireku case, there was no clear reason to depart from these findings. Unless and until a higher court (this case was heard in the Employment Appeal Tribunal, the one it relied upon was heard in the Court of Appeal) chose to address the issues differently, the previous finding re. the test of causation should be followed.

As an aside, the EAT found that Mr Mireku’s claim was bound to fail in any events as the comparator that he had relied on were not comparable full-time workers, which is contrary to the 2000 Regulations.

This case reinforces the importance of considering a claim correctly under the 2000 Regulations. It is unlawful to treat someone less favourably due to their part-time status, when compared to a suitable full-time comparator. These protections apply to several areas such as pay, leave, promotions and redundancy selection to name just a few.

Whilst Mr Mireku would have been unsuccessful in any event due to the specific facts of his case, the EAT have reiterated the test of causation that will be applied. With the part-time status needing to be the ‘sole’ reason for which someone is treated less favourably, this means that a Claimant will need to be able to demonstrate this key element when looking at a suitable comparator.

This case will continue to act as useful guidance unless and until, a more senior court interprets the legislative test differently.