Last month M&S said it would cut the payment to time-and-a-half from April next year as part of a revised rewards package (The Grocer, June 21, p15).
A spokeswoman said it had decided to revise its proposals after receiving feedback from its workers' councils, the Business Involvement Groups. However, the revision will not apply to new employees who will receive the lower rate of time-and-a-half for Sunday and Bank Holiday working.
Usdaw deputy general secretary John Hannett said: "It was clear from the large number of calls we received from disgruntled M&S staff that the workforce was very unhappy."
He added that the union had recruited more than 100 Marks and Spencer workers during the past few weeks.