Approximately 6,000 employees or former employees of Tesco Stores brought proceedings against it before the ET on the ground that they had not enjoyed equal pay for male and female workers for equal work, contrary to national legislation and Article 157 TFEU. The female claimants submitted that their work in the stores and that of the male workers employed in the distribution centres were of equal value, and that they were entitled to compare their work and that of the male workers under Article 157 TFEU, even though the work was carried out in different establishments. They contended that Tesco Stores was a "single source" for their terms and conditions of employment and for those of the male workers. Tesco Stores submitted that Article 157 TFEU was not directly effective in the context of claims based on work of equal value, so the female claimants could not rely on that provision before the ET, and it also disputed whether it could be classified as a "single source".

The CJEU held, on the request for a preliminary ruling from the ET, that the principle, laid down by EU law, of equal pay for male and female workers could be relied on directly, in respect both of "equal work" and of "work of equal value", in proceedings between individuals (that is, other than public bodies). It also observed that, where differences in the pay conditions of workers performing equal work or work of equal value could be attributed to a single source, the work and the pay of those workers could be compared, even if they worked in different establishments.