Sir John Major has said MPs should be given a free vote and allowed to order a second EU referendum.
The former Conservative prime minister used a speech on Wednesday to argue many voters now believed they had been “misled”.
“The electorate has every right to reconsider their decision,” he said.
Sir John also accused Theresa May of “bad politics” by ignoring business demands that the UK remain in the customs union and single market.
“It is only fear of Mr Corbyn and Mr McDonnell that prevents a haemorrhage of business support,” he said.
Parliament has been promised a “meaningful vote” on the final Brexit deal negotiated by May.
Sir John said the prime minister must allow her MPs to have a free vote on whether to support the deal, send the negotiators back to seek improvements from Brussels, or hold a referendum on the agreement.
A free vote would mean political parties do not order their MPs to vote how the leadership wants them to.
Sir John, who campaigned for Remain last year, said this would “minimise divisions” in the country as well as “within the political parties”.
May is facing a defeat in the Commons over her plan to pull the UK out of the customs union as pro-Remain Tory MPs plan to vote with Labour.
The prime minister today rejected the EU’s draft legal text which would see Northern Ireland remain in the customs union in order to avoid a hard border.
In a major intervention, Sir John said: “The deep divisions in our nation are more likely to be healed by a Brexit freely approved by Parliament, than a Brexit forced through Parliament at the behest of a minority of convinced opponents of Europe.
“A free vote would better reflect the reality that – for every 17 voters who opted for Brexit – 16 opted to remain in the EU.
“But, regardless of whether a free vote is offered, Parliamentarians must decide the issue on the basis of their own conscience. Upon whether, in mature judgement, they really do believe that the outcome of the negotiations is in the best interests of the people they serve.
“By 2021, after the likely two-year transition, it will be five years since the 2016 referendum. The electorate will have changed. Some voters will have left us. Many new voters will be enfranchised. Others may have changed their mind.”
Sir John added: “No-one can truly know what “the will of the people” may then be. So, let Parliament decide. Or put the issue back to the people.”