MP Siobhain McDonagh has written to the chief executive of Asda asking to clarify a number of issues around the grocer’s proposed changes to the contracts of its hourly paid staff.

Asda said last week it had put around 3,000 of its hourly paid staff into consultation over proposed changes to their contract.

The changes would see the basic hourly rate increase to £9 an hour but also see staff forgo paid breaks and would class bank holidays – other than Christmas, Boxing Day and New Year – as normal working days.

The proposals would see an increase in the “premium” nighttime shift pay rate but would shorten the length of these shifts.

McDonagh, the Labour MP for Mitcham and Morden, wrote to Asda boss Roger Burnley to express her concern at the proposed changes and called on him to clarify how the new arrangements would affect staff.

In the letter, sent yesterday, McDonagh said: “I do not believe that any proposals framed in the name of ‘fairness’ should have such negatives consequences for so many of your longstanding staff.

“A loss of paid breaks, an end to premium pay, and a shortening of the night shift will result in approximately 2,700 of your staff losing up to £500 a year, with a further 300 set to lose more than this amount.”

McDonagh also called on Burnley to explain why Asda was proposing to shorten the night shift window to just five hours – between midnight and 5am – and asked “what would happen to those staff who do not choose to sign” the new contracts.

“I am also concerned at the impact that these proposals will have on working hours, as staff will be required to be more flexible in the days and times that they work,” she said.

“Though some staff will welcome this more flexible approach to working hours, it will extremely difficult for other and those most longstanding in your organisation may have already built their lives around their fixed employment hours.”

At the time, a spokesman for the grocer said the proposed changes would leave “95% of colleagues better off overall” and it would “make sure there’s a transitional payment” for the remaining 5%.

This is not the first time McDonagh has waded in on contract disputes at a retailer. In September 2016, she criticised Marks & Spencer over a leaked internal document that showed it was prepared to cut jobs that did not accept revised payment terms.

An Asda spokesperson said: “We are currently consulting with our colleagues and their representatives over a proposal to invest in an increased rate of pay and changes to terms and conditions, which would enable us to deliver better service to our customers in an intensely competitive marketplace and would make 95% of our colleagues financially better off. This consultation is ongoing and we will always have conversations about change with our colleagues first.”