Rules on Sunday opening hours for shops in England and Wales are out of date and need to be relaxed, a group of 200 MPs and council leaders has said.
In a letter to the Sunday Telegraph, they wrote that increasing spending on Sundays would boost job prospects and help shops compete with online firms.
They backed government plans to devolve Sunday trading laws to local councils.
However, the shopworkers' union said the majority of its members opposed extended Sunday trading hours.
In the letter, the group - which includes the cross-party British Infrastructure Group (BIG) of MPs - said the world had changed "a great deal" since Sunday trading laws were last updated in 1994.
"Yet whilst times and attitudes have changed, Sunday Trading laws have stayed the same," they wrote.
"Our high streets and physical retailers have been left trying to compete with 24/7 online shopping, a task which is made harder by a shortened trading day at the weekend, just when many families might hope to go shopping together."
'Outdated retail law'
In England and Wales, shops over 280 sq m, or 3,000 sq ft, in size can open their doors for only six consecutive hours between 10:00 and 18:00. Retailers can be fined up to £50,000 if they break the rules.
There are no trading restrictions in Scotland, while in Northern Ireland shops can open for up to five hours between 13:00 and 18:00.
The letter supported a report by the BIG, which backs the modernisation of "outdated retail law".
The group includes more than 40 MPs and is led by former Conservative Party chairman Grant Shapps.
Its report argued the trend across Europe is for "liberalising" Sunday trading laws, saying that changes on the continent resulted in a 7‐9% net increase in employment.
The Sunday Telegraph letter added: "Ultimately, we believe that the best way to determine whether large shops are open for longer than six hours on a Sunday is to hand this decision to local communities.
"It is for this reason that we back the proposed change in England and Wales which would update our trading laws for the 21st Century."
Campaigners opposed to longer opening hours question if the move would really benefit the High Street, pointing out that under the existing law, smaller traders are allowed to open for longer.
Last year, Chancellor George Osborne promised that councils and mayors would get the power to set Sunday trading laws in their areas.
Business Secretary Sajid Javid earlier this month said ministers plan to press ahead with the proposal, saying the move would allow local authorities to "help struggling high streets".
However, it faces strong opposition in the Commons.
And retail union, Usdaw, has said the current trading hours give "everyone a little bit of what they want".
"Retailers can trade, customers can shop, staff can work; whilst Sunday remains a special day, different to other days, and shop workers can spend some time with their family," general secretary John Hannett said.