Theresa May has been dealt a heavy blow in her bid to secure new reassurances from fellow EU leaders over her Brexit deal, as the European Commission president declared there was "no room whatsoever for renegotiation".
Jean-Claude Juncker said the Withdrawal Agreement on offer was the "best deal possible" and the "only deal possible" as the Prime Minister embarked on emergency Brexit talks with her Dutch counterpart Mark Rutte in The Hague.
He offered a glimmer of hope to Mrs May by saying there was room to give "further clarifications and further interpretations without opening the Withdrawal Agreement".
The Prime Minister will also meet German Chancellor Angela Merkel on Tuesday in her bid to gain reassurances on the exit deal from European leaders ahead of a crunch EU summit on Thursday, after leaving Westminster in turmoil.
Mrs May's move to abandon a crunch Commons vote, scheduled for Tuesday, on her Brexit deal drew howls of condemnation from the opposition as well as a number of Tories.
Mr Juncker won applause from MEPs as he said: "There is no room whatsoever for renegotiation, but of course there is room if used intelligently, there is room enough to give further clarifications and further interpretations without opening the Withdrawal Agreement.
"This will not happen: everyone has to note that the Withdrawal Agreement will not be reopened."
He confirmed he would meet Mrs May on Tuesday evening but reiterated: "The deal we have achieved is the best deal possible – it is the only deal possible."
I will meet @theresa_may this evening in Brussels. I remain convinced that the #Brexit deal we have is the best – and only – deal possible. There is no room for renegotiation, but further clarifications are possible.
— Jean-Claude Juncker (@JunckerEU) December 11, 2018
It came as Commons Leader Andrea Leadsom suggested Mrs May was seeking changes that would give Parliament an additional "democratic ability to decide".
"That might include an addendum to the Withdrawal Agreement that sets out that Parliament will vote prior to going into a backstop, should that prove necessary, and potentially that the EU parliament and UK parliament must vote every year thereafter to provide that legitimacy for the UK to stay in the backstop, should that prove necessary," she told BBC Radio 4's Today programme.
"So there are plenty of options for the PM to talk to the EU about that don't involve reopening the Withdrawal Agreement, but that would provide the legal text as a part of the Withdrawal Agreement, through perhaps an addendum."
Mrs May, who is facing repeated calls from leading Tory Brexiteers to be replaced as PM, was forced to abandon the Commons vote as the scale of opposition to the Brexit deal, especially regarding proposed backstop arrangements for the Irish border, threatened a crushing rejection of her plans.
As anger at Westminster continued to fester over the PM's move to cancel the Brexit vote, MPs were poised for an emergency debate on the situation on Tuesday.
International Trade Secretary Liam Fox said it would be difficult to get the Brexit deal through Parliament without reassurances the UK would not be "trapped" in backstop measures ensuring no return to hard border in Ireland.
The backstop would see the UK obey EU customs rules after a transition period if a wider trade deal has not been agreed with the EU by then.
Referring to Mrs May's lobbying mission in Europe, Dr Fox told BBC2's Newsnight: "My colleagues will want to see that their fears of being trapped in a backstop cannot be realised.
"Without the ability to genuinely reassure my colleagues that they could not legally be kept in the backstop against their will, it will be difficult to get this through the House of Commons."
With Jeremy Corbyn under pressure from a significant number of MPs and peers to force a confidence vote on the Government, Labour former Cabinet minister Lord Mandelson said the opposition had not laid a glove on the Government.
He told the BBC: "I think the Labour Party, the Labour leadership, is facing a bit of a dilemma.
"I mean, they want to straddle, and retain the support of the third of Labour voters who backed Leave in 2016, and the two-thirds of Labour voters who backed Remain.
"Well, what happens when you, you know, ride two horses like that, you end up doing the splits."