Morrisons has become the latest big four grocer to be targeted by lawyers over alleged unequal payments to staff.

The supermarket giant could face a bill worth up to £100m in back pay after law firm Roscoe Reid said “hundreds” of current and former Morrisons workers had contacted it regarding the issue.

According to The Sunday Times, Roscoe Reid has launched a claim in collaboration with workers’ rights group Pay Justice.

The law firm claims that Morrisons’ shopfloor staff were paid less than warehouse employees for work of “equal value”.

The majority of claimants are female shopfloor workers, who insist they were paid less than male colleagues in distribution centres for performing equivalent roles.

The basis for the claim is that shopfloor workers were “systematically underpaid” by as much as £2 an hour.

The law firm believes the number of workers potentially in line for compensation could number as many as 25,000, including employees who have left within the past six years.

Morrisons’ big four rivals Tesco, Asda and Sainsbury’s are all being targeted in similar pay claims.

The claim against Tesco, which is being led by lawyers at Leigh Day, could leave Britain’s biggest retailer facing a £4bn backpay bill.

Morrisons insisted it had not yet received a legal claim. A spokesman told the FT: “Our aim is to pay our colleagues fairly and equally for the job that they do, irrespective of their gender.”

Roscoe Reid plans to begin proceedings in the next few months, initially through lodging claims with ACAS.

If given the green light by the body, the next stage would be to take the claim to an employment tribunal.