Ministers are to press ahead with plans to allow councils in England and Wales to relax Sunday trading laws.
Business Secretary Sajid Javid said the move would allow local authorities to "help struggling High Streets".
He told MPs the policy, previously reported to be facing strong opposition in the Commons, would be added to the government's Enterprise Bill.
Unions said ministers were "behaving disgracefully by trying to change Sunday trading by the back door".
Devolving Sunday trading laws to councils was first announced by George Osborne in the July Budget, and a consultation into the change closed in September.
Small shops - up to 280 sq m - are currently entitled to open when they want, but on Sundays, larger stores are restricted to six hours between 10:00 and 18:00.
In the Commons, Mr Javid's Labour shadow Angela Eagle criticised the way the government was seeking to make the change and as well as what she said was a lack of detail.
She accused Mr Javid of a "gross abuse of power" asking why the plans were being added "at this late stage" rather than being in the Bill from the start.
Mr Javid said the government's intentions "have been clear" and said amending the Enterprise Bill, which is currently making its way through the Commons, was "the right vehicle to make those changes".
He told MPs the decision to change Sunday trading hours would be "entirely local", adding: "If the people of Bromsgrove or Barking say they want to see longer Sunday opening hours, who are we here in Westminster to stand in their way?"
Under the proposals, local authorities will be able to restrict the longer hours to certain zones - such as High Streets and city centres, the Department for Business, Innovation and Skills said.
It promised that shop workers who wanted to "opt out" of working on Sundays would be able to do so, for example on religious or family grounds.
The response to the consultation would be published "shortly", the government said.
Retail union Usdaw said MPs should be able to "properly consider" the views expressed in the consultation.
General secretary John Hannett described the current Sunday Trading Act as a "great British compromise, which has worked well for over 20 years and gives 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."