Senior ministers are reportedly mulling a "plan B" for leaving the European Union if Theresa May's deal is voted down by MPs.
European leaders have approved the prime minister's Brexit blueprint at a special summit in Brussels on Sunday, which was brought back from the brink after Spain threatened to "veto" progress due to concerns over Gibraltar.
However Ms May faces an arguably more difficult task of getting her deal through parliament in the coming weeks, amid renewed opposition from both Brexit and pro-EU wings of the Conservative Party, as well as her DUP allies, Labour, the Liberal Democrats and the SNP.
Ms May is facing threats from all sides amid speculation of a fresh threat within her cabinet from chancellor Philip Hammond, who would lead an exodus of pro-EU ministers if the prime minister ends up pursuing a no-deal Brexit.
And another group of cabinet ministers are said to be in talks with the DUP to draw up an alternative plan around a 'Norway option', in which Britain stays in the European Economic Area (EEA) in case the deal is rejected.
A DUP source told the Sunday Times it was in talks with "people who might assert themselves", adding: "At that point people in the cabinet will say we've got to have a plan B. They will have our support in taking a different approach."
Party leader Arlene Foster did not deny the report, telling the BBC's Andrew Marr Show: "There are conversations going on right across government, I don't think that will surprise you.
"We are talking to everybody across government, we are talking to people in the Remain side, we are talking to Brexiteers, we are talking to everyone as I think you would expect us to do."
The Northern Ireland party has called on Ms May to “bin” the deal and threatened to torpedo their confidence-and-supply agreement, which props up her government.
In interviews ahead of DUP's annual conference on Saturday, Ms Foster claimed Ms May’s deal would be a worse outcome for the UK than a Jeremy Corbyn-led government – despite their longstanding differences.
She warned that her party would revisit its confidence-and-supply deal to support the Conservatives at Westminster if the Brexit agreement is voted through parliament.
However European Commission president Jean-Claude Juncker warned restive MPs that the EU would not budge on its plans.
Speaking to reporters as he arrived at the summit, Mr Juncker said: "This is the deal. It's the best deal possible and the EU will not change its fundamental position when it comes to these issues.''
Meanwhile, Mr Hammond and four other ministers including Amber Rudd, David Gauke, Greg Clarke and the PM's de-facto deputy David Lidington could resign rather than be associated with a no-deal Brexit, according to the Mail on Sunday.
Mr Hammond delivered a gloomy verdict of the economic prospects of leaving the EU without a deal on Saturday, telling the BBC that a no-deal Brexit would unleash "economic chaos".
He said: "If the meaningful vote is lost we are in uncharted territory.
"We will be faced with potential economic chaos, I am sure we would get a very negative reaction from the business community, from investors, from the markets.”
On the eve of the summit, Ms May made an emotional appeal to the nation, saying her deal would deliver “for our whole country and all of our people, whether you voted ‘Leave’ or ‘Remain” and promising a “moment of reconciliation” when Britain leaves the EU.
In an open letter to the British public, Ms May said the deal will “honour the result of the referendum”, taking back control of UK borders, money and laws, and taking the country out of EU programmes “that do not work in our interest”.
She also made a plea for unity and said Brexit day next year will be “a moment of renewal and reconciliation for our whole country ... when we put aside the labels of ‘Leave’ and ‘Remain’ for good and we come together again as one people”.
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