Sunday trading laws in England and Wales have been suspended until the end of the Olympics and Paralympics, the BBC reported.
The government said being able to open longer on a Sunday would help retailers generate tens of millions of pounds in increased profits during London 2012. However, shop staff will retain the right to opt out of working on a Sunday.
Under current legislation shops of more than 280 square metres (3,000 square feet) can open for a maximum of six hours on a Sunday, and only between the hours of 10:00 and 18:00.
A spokesman for the Department for Business, Innovation and Skills said larger shops would be "free to choose their opening hours on a Sunday" with "no restrictions on these hours" until the Olympics and Paralympics were over on September 9.
Chancellor George Osborne said the move would help maximise the economic benefits of the Olympic Games beginning on July 27.
At the launch of Transport for London's plans for the Games, officials spoke about 11 million visitors.
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Shop workers' union Usdaw and the Keep Sunday Special campaign warned that the suspension could set a precedent.
John Hannett, general secretary of the union, said: "Usdaw remains vehemently opposed to the deregulation of Sunday trading and we expect the government to abide by its commitment that this summer's temporary suspension will not lead to any further attempts to extend Sunday opening hours.
"The government failed to make a coherent business case for the suspension and there is no evidence that it will boost the economy or tourism.
But the government insisted it had no plans to relax the rules permanently.
Business minister Norman Lamb said: "The Olympic and Paralympic Games are almost upon us and you can sense the excitement building.
"This will be a fantastic opportunity to showcase, not just London, but the whole of the country to the rest of the world and provide a boost for the economy, sales and employment," the BBC quoted Lamb as saying.
"I want employers to work with their staff so that we can all make the most of the Olympics.
"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," Lamb said.