Suppliers have reacted angrily to a demand for a contribution to Marks & Spencer's pre-Christmas promotional campaign.

In a letter to food suppliers sent by head of food John Dixon and seen by The Grocer, M&S asked suppliers to support its Spend and Save voucher promotion in which shoppers receive a £5-off voucher when they spend £30.

"As the year draws to a close we want to maximise our growth and take full advantage of the Christmas opportunity when we attract many more 'occasional' customers and see our market share increase," wrote Dixon.

"You will remember the success of our Spend and Save campaign last December and January, improving our rate of growth, and we entirely supported this ourselves."

The letter, dated 1 December, informed suppliers that M&S would repeat the campaign in the week before Christmas this year. "We would like you to demonstrate your continued support by sharing the cost with us," it said.

It did not give details of how much suppliers would have to contribute, but said it had calculated the suppliers' share of the sales benefit and therefore the respective cost. Suppliers were advised to contact their category manager or buyer to finalise details by 15 December.

One M&S supplier told The Grocer it had received the letter but that it would not be supporting the activity. "If something is in our interest as well as M&S's, we'll look at it, but if we think it's just M&S looking to fund a new campaign then we won't support it," a spokesman for the supplier said. "In this case it looks like M&S looking to fund a new campaign."

Another said it always tried to work with retail customers but that this would only benefit M&S.

However a spokeswoman for M&S defended the letter. "This is normal industry practice and part and parcel of trading negotiations with our suppliers," she said. She also expressed surprise that suppliers didn't believe it would benefit them.