Liberalisation of Sunday trading laws is set to pass as the Scottish National Party withdrew their opposition after a "dirty deal" with the Conservative government.

The changes would allow local authorities to remove current limits on opening hours for large stores on a Sunday, making it like any other day of the week.

The proposals have faced sustained opposition from Christian groups, unions and a coalition of organisations under the Keep Sunday Special campaign. They were initially withdrawn in November after 20 rebel Tories, led by Christian MP David Burrowes, joined with Labour and SNP MPs to oppose the government.

However the changes, which are the biggest to Sunday trading laws in over 20 years, were re-introduced early in 2016, prompting rumours of a SNP-Tory alliance.

It has emerged over the weekend the SNP has dropped their opposition, with Labour's Angela Eagle accusing them of a "dirty deal" to get more powers for Scotland.

"It's hard to avoid the suspicion that the SNP have not been playing their own games and doing a dirty deal with the Tory government to get what they wanted on the fiscal framework in return for throwing the shop-workers to the wolves," said the shadow business secretary.

Without the SNP's backing, an amendment to the Enterprise Bill which would remove the Sunday trading changes will almost certainly fail.

When the proposals were first tabled in November, the SNP's Westminster leader Angus Robertson said "this legislation will impact on workers in Scotland and elsewhere in the UK and no pay safeguards have been offered by the Westminster government.

"The SNP will continue to work with the representatives of shop workers and we will oppose the Tory proposals," he continued. The SNP's initial opposition was thought to be based on research showing Scottish shop workers would lose up to £1,400 per year under the change.

Although no pay safeguards have been introduced, Hannah Bardell MP, SNP business spokesperson, hinted their position has changed.

"As is well known we have had Sunday Trading in Scotland for some time and the SNP have never been opposed to the principle of Sunday Trading," she said.

"However, our initial concern and opposition was primarily around the potential knock on impact to Scottish workers of any changes in England & Wales to Sunday Trading.

"The SNP welcome the provision for additional employee protections that the UK Government has brought forward in new schedule 1 of the Enterprise Bill; which amends the Employment Rights Act to, amongst other provisions, protect any worker from being forced into working on a Sunday.

"Without the strong and principled action of the SNP, such protections may never have materialised. On behalf of the SNP I have met with and engaged with a wide range of interested stakeholders in recent weeks and will continue to do so in the run up to report stage of the Bill before we reach a final position."

David Burrowes, who has led the Tory rebellion against the changes said the apparent concessions to the bill "still don't negate widespread concerns".

"If they [the SNP] are consistent with what they said in November, they will [oppose it]. What happens south of the border will also happen north," he said in the Times.

The blow to the Keep Sunday Special campaign was dealt after senior Roman Catholic, Church of England, Church in Wales, Methodist, United Reform Church and Salvation Army figures issued a joint statement opposing the plans. They warned of the "commodification" of modern life in a letter to The Telegraph.

"We are concerned that the further deregulation of Sunday Trading laws is likely to disrupt the rhythms of community life that are so integral to the common good," the letter wrote.

"In a world of increasing commodification the space for shared time and activities, central to human flourishing, is becoming increasingly rare. Needlessly extending Sunday opening hours will only exacerbate this trend."

The letter argues the current compromise reached in the 1990s offer "a balance" and there is "no evidence base" to show the changes will lead to "substantial economic benefit".

However the business secretary, Sajid Javid, has said relaxing the restrictions would enable local areas to help "struggling high streets".