Theresa May is under renewed pressure from Brexit supporters to secure fresh concessions on the Northern Irish backstop, as Dublin warned there was no room for manoeuvre on the issue.
As the Prime Minister faced another Commons showdown over her EU withdrawal agenda on Tuesday, Downing Street was battling to keep control of the Brexit timetable.
In a pointed intervention, Boris Johnson insisted he had it from "senior sources" the PM was planning to go to Brussels to renegotiate the backstop and win a "freedom clause".
However, Ireland’s deputy prime minister Simon Coveney insisted there would be no changes to the Withdrawal Agreement which states the UK will obey EU customs rules if no wider deal has been struck after a transition period.
Mr Coveney said the backstop was crucial in preventing a hard border.
He told the Press Association: “Peace and the Good Friday Agreement are more important than Brexit.
“Even in a no-deal Brexit situation every party and every MP in the UK will have a responsibility to ensure there is no return to a hard border and Northern Ireland is protected.
“That won’t be easy and those who misrepresent the backstop don’t have an alternative to it.”
Mr Coveney’s comments were seen as a swipe at Tory Brexit supporters hoping to use Commons amendments on Tuesday to try and force a change in direction on the backstop.
Attention is focusing on an amendment by Tory grandee Sir Graham Brady which calls for the removal of the backstop and “alternative arrangements” to be put in its place.
Brexiteers say if the non-binding amendment is passed it will give the prime minister more leeway to win concessions from the EU.
Sir Graham, who is chairman of the highly influential 1922 Committee of backbench Tory MPs, told the BBC: “My amendment is an attempt to bring the kind of compromise forward that can actually attract the support of a majority of the House of Commons.
“I hope it will on Tuesday, and demonstrate in terms to the EU that there is a way forward.”
Meanwhile, pro-Europe amendments pose a threat to Mrs May’s grip on Brexit.
The Government is thought to be particularly concerned about a cross-party backed amendment put forward by Labour’s Yvette Cooper which is aimed at stopping a no-deal exit and paving the way for keeping the UK in the EU until the end of the year.
The Daily Telegraph reported that the PM is seeking to see off the threat of a Tory rebellion, and the possibility of ministerial resignations, by considering whether to hold a “meaningful vote” on Brexit within the next fortnight.
A dozen pro-European ministers including Work and Pensions Secretary Amber Rudd and Justice Secretary David Gauke held a conference call in which they agreed such a move would help defer a potential rebellion, according to the newspaper.
Writing in the Daily Telegraph, Mr Johnson called on the PM publicly to confirm a “change of heart” on the withdrawal deal.
He said: “That backstop is dead, rejected by the biggest ever parliamentary majority; and that is why I hope and pray that I am right about the intentions of Number 10.
“If we mean it, if we really try, I have no doubt that the EU will give us the Freedom Clause we need.
“And if the PM secures that change – a proper UK-sized perforation in the fabric of the backstop itself – I have no doubt that she will have the whole country full-throatedly behind her.”