Sir John Major has called for Article 50 to be revoked immediately for “serious and profound reflection” by parliament and the people.
The former Tory prime minister said Theresa May needs the “precious commodity” of more time to sort out Brexit as the crisis over EU withdrawal threatened to engulf the government on Tuesday.
In a separate development in Westminster, Tory MP Nicky Morgan has called for opposition parties to join a national unity government - something which was last resorted to by Winston Churchill during the Second World War.
May was forced into an extraordinary climbdown on Monday when she delayed the meaningful vote on her Brexit deal, acknowledging she faced a resounding defeat.
But Major, who also faced a revolt inside the Conservative Party over Europe, has appealed to his successor to pause the Brexit process.
Speaking at an international affairs think tank in Dublin, he said: “We need to revoke article 50 with immediate effect. The clock, for the moment, must be stopped.
“It’s clear we now need the most precious commodity of all: time. Time for serious and profound reflection by both parliament and people. There will be a way through the present morass, there always is.”
The European Court of Justice ruled on Monday that the UK can unilaterally revoke A50, the UK’s official notice it is leaving the EU, should it wish.
Brexit Secretary Stephen Barclay told MPs on Monday there were no plans to revoke A50 and that ministers planned to honour the result of the 2016 Brexit referendum.
Morgan, a former education secretary, told MPs on Tuesday afternoon that “parliament must step in” to avoid the UK crashing out the EU without a deal.
“Maybe its time for some sort of government of national unity,” she said.
“Maybe it’s time for a free vote in an eventual vote on the deal - avoiding usual party political constraints.
“With 108 days to go until this country leaves the EU, if the government can not sort this out on this matter of great national importance, then parliament must step in.”
Major led Britain from 1990 to 1997 and faced down Eurosceptic members of his own cabinet to win a vote of confidence over his handling of the Maastricht Treaty in 1993.
He has said he believed Brexit reduced Britain’s international influence.
“We are a more valued ally for America because of our influence in Europe and we are more valued by Europe because of our close relationship with America,” he said.
“Britain, shorn of both these long-standing allies, will be seen by the world as a mid-sized, middle-ranking power that is no longer super-powered by her alliances.”