Sainsbury’s does not want Sunday trading hours to be extended on a permanent basis despite seeing “great trading” throughout the Olympics in the grocer’s stores that were open longer.

The news comes as shopworkers’ union Usdaw writes to Business Secretary Vince Cable to “seek urgent assurance that the Government has no plans to permanently deregulate Sunday trading hours in England and Wales”.

The move comes after speculation over the weekend that the Conservatives were open to extending Sunday trading hours on a permanent basis.

The Government relaxed Sunday trading hours for six weeks from the start of the Olympics period to take advantage of a potential increase in footfall. Retailers could opt to trade for 24 hours a day. Ordinarily they would only be allowed to trade for six hours on a Sunday.

A Sainsbury’s spokeswoman said the grocer took a “targeted approach”, extending opening hours at stores affected by Olympic events, with 30 of its 1,000 stores taking advantage of the relaxation in the law.

“We saw some great trading at those locations and were very pleased to be able to serve the unusual customer demand associated with the Games,” said the Sainsbury’s spokeswoman.

“That said, we don’t believe people are looking for Sunday trading to be extended on a permanent basis, with both customers and colleagues seeing the current status quo as a good British compromise.”

John Hannett, general secretary of Usdaw, which would oppose any move to make the relaxation permanent, said: “Longer Sunday opening hours won’t put more money in the pockets of hard pressed shoppers and there is no evidence it would boost jobs or growth.

“It would however have a very detrimental impact on the family and caring commitments of our members.

“With margins being squeezed and sales flat lining, the last thing the retail sector needs at the moment is the prospect of increased overheads for little or no return.

“If the Government really wants to boost retail and the economy as a whole then it would be much better advised to immediately reduce the rate of VAT.”

Original Factory Shop chief executive Angela Spindler said: “We don’t feel like they were deferred sales. We definitely saw a big step up in Sunday trading. This was particularly seen in our coastal stores. It’s about giving customers the flexibility to shop when they want to.

“I do believe in keeping Sunday special but if there is a huge benefit to be had by keeping the law permanently relaxed then it might be worth pursuing.”

Schuh head of retail Phil Whittle said: “We really got behind it but reassessed it during the period. The smaller more provincial centres hadn’t generated enough to justify [later opening] but in the big city centres it was very worthwhile. I hope the Government sits up and notice, surely there’s a case for letting customers vote with their feet about when they shop. In recessionary times we could do with taking unhelpful bureauracy out of the equation.”

Fat Face chief executive Anthony Thompson come out against the potential permanent change to the law. He said: “Most of our stores are under the legal limits but it will be interesting to see how it has affected Big Box retailers. It was wise to extend them over the Olympics. With Stratford there were times when if we didn’t open until 11 or 11.30 we would have burst but I’m not in favour of extending trading hours permanently.

“There are plenty of trading hours for retailers to enjoy, I don’t want our staff to feel forced into working longer hours. It’s not a positive thing for families if it’s dramatically relaxed. But once you open the door it is difficult to close it, there will be growing pressure to make the changes permanent.”