Clause 4, The Principle of Non-Discrimination, of the Framework Agreement on Part-Time work implemented by the Part-Time Workers Directive 97/81/EC and extended to the United Kingdom by Directive 98/23/EC states:

“In respect of employment conditions, part-time workers shall not be treated in a less favourable manner than comparable full-time workers solely because they work part time unless different treatment is justified on objective grounds”.

In this case British Airways sought to appeal a decision of the employment tribunal upholding a claim by Mrs Florence Pinaud that she had been treated less favourably than a full-time worker, contrary to the Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000. The claimant argued she was required to be available for 3.5% more days than her full-time counterpart, for the same pay, and that this amounted to less favourable treatment as regards the terms of her contract. She said she was “regularly required” to work more duty hours proportionately than her full-time equivalent.

British Airways claimed the bidding system created the inconsistency and that the requirement to be available for a number of additional days throughout the year was trivial and of “minimal” impact. The employment tribunal rejected this, stating “the requirement to be available for work for an additional 8.5 days over the course of a year was a significant period”.

On appeal the respondent argued the employment tribunal had erred in:
1. it’s application of the pro rata principle;
2. making a comparison of available hours rather than weekly hours worked;
3. on the question of justification, holding that statistical evidence was irrelevant to its decision.

The Employment Appeal Tribunal rejected the grounds of appeal, stating the tribunal had correctly compared days of availability and made no comparison of weekly hours. It accepted the employment tribunal had applied the correct principles relating to justification, however, it said it was wrong in law to regard the statistical evidence produced by the parties as irrelevant…

“The fact that the Claimant had to be available to work on proportionately more days was the feature that required justification. Its existence did not rule out an enquiry into the extent to which it impacted on her so that a conclusion could be reached on whether the measure was proportionate”.

The finding of less favourable treatment was upheld but the question of justification was remitted to a freshly constituted tribunal.

*The GB regulations are equivalent to the Part-time Workers (Prevention of Less Favourable Treatment) Regulations (Northern Ireland) 2000.
http://www.bailii.org/uk/cases/UKEAT/2017/0291_16_0108.html