Extending unrestricted Sunday trading beyond the summer would be a "major breach of trust" by the Government, a Tory MP has warned amid reports ministers are keen on the move.
Mark Pritchard said he would oppose prolonging an eight-weekend extension brought in for the duration of the Olympic and Paralympic Games in a bid to capitalise on the influx of visitors.
Larger stores have been allowed to ignore the usual stipulation that they can open for a maximum of six hours between the hours of 10am and 6pm thanks to emergency legislation. The law was approved by the Commons after ministers guaranteed that it would not be used as a "Trojan horse" for the introduction of a permanent relaxation.
Trade unions oppose such a change as it would place pressure on staff to work on Sundays and there is also a vociferous lobby by religious groups who want to keep the day "sacred".
The Sunday Telegraph said senior Conservative ministers wanted to include unrestricted trading in a Bill in the autumn of measures to stimulate urgently-needed economic growth.
Communities Secretary Eric Pickles told the newspaper he was "willing to look and see what the difference in trading patterns were" during the period of the Games, adding: "I'm always keen that we respect peoples' religious beliefs. But I think we should kind of look long and hard at the results."
But hailing the temporary measure when it was introduced, Liberal Democrat business minister Norman Lamb said: "I want to make it clear that this is a temporary measure and not a test case for a permanent relaxation of the rules in the future."
Mr Pritchard said: "This is a major breach of trust between the Government and the many Conservative MPs who only supported the measure because the Government promised the change would be temporary only.
"A permanent change would harm small traders, workers' rights, and further damage relations between the Church and the Government. I will not support the move."
Speaking at a press conference in Downing Street, Prime Minister David Cameron said: "We said at the time it was a specific thing for the Olympics and that was the proposal that we made."