Theresa May has come under pressure to intervene in a dispute between Sainsbury’s and its shop floor workers over the supermarket’s plans to overhaul staff contracts.

A group of high profile MPs has written to the Prime Minister, urging her to face down the grocery chain’s chief executive Mike Coupe and force him to “ensure that no staff will face a pay cut”.

Sainsbury’s is scrapping paid breaks and premium pay on Sunday for thousands of staff.

While the supermarket is simultaneously increasing basic pay, it is thought that 13,000 workers will lose out to the tune of £3,000 per year as a result of the changes.

Penned by Labour’s Siobhain McDonagh MP and backed by the likes of Labour’s David Lammy, Frank Field and shadow business secretary Rebecca Long Bailey, and Tory Robert Halfon, the letter describes Sainsbury’s actions as “deplorable”.

The letter, seen by the Press Association, reads: “We are completely dismayed that a company of Sainsbury’s reputation would use an increase in basic pay as a smokescreen for a whole array of deplorable decisions that will hit hardest their most dedicated, loyal and long-term staff.

“Under the proposed changes, all employees will lose their paid breaks, there will be widespread cuts to premium pay including a shortening of nightshift premium hours and a scrapping of Sunday premium pay, and shop floor staff will no longer receive bonuses.

“However, the scrapping of the bonus scheme will not affect the CEO, Mike Coupe, or his fellow management team.”

The letter has received the support of around 100 MPs and represents a major test for Mrs May, who last year backtracked on a promise to put company workers on boards.

Simon Roberts, retail and operations director for Sainsbury’s, said: “We don’t believe that this letter accurately reflects how the vast majority of our colleagues are feeling.

“We have conducted meaningful consultation with around 100 colleague representatives and have made a number of changes to our original proposals based on their feedback.

“It is extremely disappointing that our plans to make Sainsbury’s colleagues the best-paid in retail are being deliberately misrepresented to such a degree and we would be happy to set the record straight.”

In Prime Minister’s Questions last week, Ms May was asked whether she saw the contract changes as an “insult”.

Mrs May said she would look at the issue, but that “these are commercial decisions that are taken by the employer and by Sainsbury’s”.