A landmark Supreme Court ruling has reshaped the legal landscape for part-time workers (PTWs), establishing that less favourable treatment claims do not require proof that part-time status was the exclusive cause of an employer's decision.
Background:
The dispute arose in 2016 when a professional private hire driver operating within a small transport enterprise challenged the fairness of the company's fee structure. The worker, who operated on reduced hours, was required to pay a fixed weekly circuit fee to access the company's booking and dispatch system. As the fee was charged at a flat rate, regardless of the number of hours worked, part-time drivers incurred a significantly higher hourly cost burden than full-time drivers for using the same infrastructure. The driver brought a claim alleging less favourable treatment on the ground of his part-time status, invoking the Part-Time Workers (Prevention of Less Favourable Treatment) Regulations (PTWRs) 2000.
An Employment Tribunal had initially dismissed the claim, concluding that the circuit fee was implemented to generate business revenue rather than penalise part-time schedules, and asserting that the statute required part-time status to be the sole ground for the differential treatment.
Although later appellate courts agreed that part-time status was a contributing factor, they felt bound by older Scottish Court of Session precedent, which interpreted the law as requiring a sole-cause test. The matter ultimately proceeded to the Supreme Court for final determination.
Decision:
The Supreme Court unanimously allowed the appeal, holding that a PTW alleging discrimination under Regulations 5(1) and 5(2) of the PTWRs 2000—enacted pursuant to Section 19 of the Employment Relations Act (ERA) 1999 to implement Directive 97/81/EC and the underlying framework agreement—need not establish that part-time status was the sole reason for the treatment. Overruling McMenemy v Capita Business Services Ltd [2007] and preferring the approach in Sharma v Manchester City Council [2008], the Supreme Court ruled that the established domestic anti-discrimination standard applies, in that it is sufficient if the protected status is an effective cause or else holds a significant influence over the outcome. The deliberate omission of the phrase "solely because" in the domestic regulations reflected an intention to apply standard effective cause jurisprudence.
Implications:
This ruling carries profound practical consequences for employers and employees alike, offering robust reassurance to individuals working reduced hours across various industries. Businesses must carefully review their operational policies, remuneration structures, fee systems, and employee benefits to ensure that practices applied universally do not inadvertently disadvantage PTWs. Employers can no longer defend indirect or mixed-motive differential treatment simply by pointing to a secondary commercial justification, such as administrative convenience or general revenue generation, as proof that part-time status was not the exclusive driver of the policy.
For workforce participants, the judgement reinforces the principle that flexible working arrangements (FWAs) should not carry hidden financial or professional penalties. When organisations introduce flat-rate charges, mandatory fees, or proportional benefit restrictions, they must be fully prepared to objectively justify any resulting disproportionate impact on part-time staff. Ultimately, the decision promotes fairness and legal clarity, ensuring that legislative protections for flexible employment cannot be easily circumvented by pointing to a panoply of contributing business factors.
