The Keep Sunday Special campaign is urging retailers to attend a mass lobby of Parliament on Monday in a bid to persuade MPs to vote against changes to Sunday trading legislation.

The changes the government proposes would allow stores bigger than 3,000 sq ft to stay open for more than the current six hours on a Sunday with the power to make the final trading decision devolved to councils and mayors.

The appeal to lobby MPs by KSS, whose members include the Association of Convenience Stores, shopworkers union Usdaw, the Federation of Wholesale Distributors, the National Federation of Retail Newsagents and the Church of England, came after leaders of 150 local councils and 40 MPs wrote a letter to a Sunday newspaper calling on the government to press ahead with a compromise measure to allow councils to decide on zones for relaxing Sunday trading hours.

The members of the British Infrastructure Group, led by Grant Shapps MP, argued the status quo was “archaic” and prevented high street retailers from competing more fairly against online shops.

“With UK shoppers turning ever more to the internet to satisfy their flexible and convenient shopping needs, it no longer makes sense for large shops to be restrained by limiting their opening hours,” said Shapps.

The British Infrastructure Group has published a report, Sunday Trading: Saving the Great British High Street. It concludes that modernised trading laws could provide economic benefits worth £1.4bn annually to the overall UK economy and £64 to each family.

ACS chief executive James Lowman said there was nothing new in the “re-heated” report, which used data from the government’s review of Sunday trading in 2006 and analysis of Sunday trading policy in other countries from as far back as 1972.

“This evidence has already been used in the government’s consultation and has been thoroughly discredited,” he said.

“Grant Shapps’ argument is based on the idea that more Sunday trading hours would lead to more trade. This is simply wrong.”