A group of West Cumbrian supermarket workers who believe they have been underpaid could be owed up to £1.45m.

Lawyers at Leigh Day solicitors are acting on behalf of 145 people who work in 12 supermarkets part of Asda, Sainsbury’s, Tesco, Morrisons and the Co-op chains in Workington, Cockermouth and Whitehaven.

The solicitor firm’s claim against the supermarket giants is on behalf of hourly paid store-based staff, mainly women, who claim their work is of equal value to that of workers, mainly men, who work in the supermarkets’ distribution centres.

The difference in hourly pay for a shop floor worker and a distribution centre worker at the big five supermarkets can range from £1.50 to £3.

Lawyers believe the average worker could be entitled to £10,000 in back pay up to six years.

Chris Benson, who leads the equal pay team at Leigh Day, said: “Despite equal pay laws being in place for almost 50 years, our clients believe they are still unlawfully underpaid.

“Our clients believe that store and distribution jobs are equally important to the big five supermarkets and should be paid equally. This case is not about whether the jobs are identical or even the same; it is saying they are of equal value.”

Leigh Day is handling claims for more than 45,000 supermarket workers nationally.

In the Carlisle area they have 115 claimants working across 12 stores.

A Co-op spokesman said: “We have received a small number of equal pay claims. Unlike some of the bigger food retailers, we do not have large scale multiple claims. It wouldn’t be appropriate to comment on individual claims, but we will be defending these claims and are confident that our reward practices are fair.”

A spokesman for Asda said: “Our hourly rates of pay in stores are the same for female and male colleagues and this is equally true in our depots. Pay rates in stores differ from pay rates in distribution centres because the demands of the jobs in stores and the jobs in distribution centre are very different; they operate in different market sectors and we pay the market rate in those sectors regardless of gender.”

A Tesco spokesman said “We work hard to ensure that we reward our colleagues fairly for the jobs they do. The pay in our stores and in our distribution centres is the same for colleagues doing the same jobs regardless of gender.

“There are fundamental differences between the jobs in our stores vs those in distribution centres. These differences, in skills and demands, as well as the different markets in which they operate, do lead to variations in rates of pay between stores and distribution centres – but these are not in any way related to gender, and we will strongly defend these claims.”