There is no sense of there being just five days to save Theresa May's tenure as Prime Minister, No 10 has insisted, as Tory rebels and the Democratic Unionists rejected a move at a compromise Brexit Plan.

As some 30 ministers travel to the four corners of the UK to sell the Prime Minister’s deal with Brussels, dubbed a “desperation strategy,” Downing St again refused to say if Mrs May was confident she could get it through the Commons in Tuesday’s crunch vote.

And Boris Johnson suggested the Prime Minister’s Brexit deal was similar to the “kind of diktat” that might be imposed on the defeated side in a war. It would, he argued, lead to France using it to "plunder" UK fishing waters.

Asked if she was, her spokesman replied: “It’s ultimately for MPs to decide how they cast their vote. She believes it’s the right deal for the country, it delivers on the Brexit that the people voted for and does it in such a way that protects jobs. She absolutely believes it’s the right deal for the country.”

Speculation has been mounting over the future of the Prime Minister, with fears that a heavy defeat of her Brexit Deal in the Commons could result in a vote of no confidence in the government from Labour, a decision which has been echoed by Jeremy Corbyn.

There has also been speculation of a vote of no confidence from her own party in the event of a heavy defeat.  

Asked if there was any sense that there were just five days to save the Prime Minister's premiership, he replied: “No.”

With three days of the five-day Commons debate complete, analysis by the Press Association shows of 163 MPs who have spoken, just 27 have indicated they will back Mrs May's deal compared to 122 - including 29 Tories - who will vote against it.

On Thursday night, three Conservative MPs tabled an amendment, said to be with Downing Street's backing, effectively placing a one-year time limit on the backstop arrangement, meant to avoid a hard border in Ireland, and giving MPs the choice to extend the transition period.

Mrs May’s spokesman suggested there was no Downing St connivance, stressing: “It’s a backbench amendment.” He indicated it would be considered in the usual way.

Already the DUP’s Arlene Foster has rejected the move, tweeting: "Domestic legislative tinkering won’t cut it. The legally binding international Withdrawal Treaty would remain fundamentally flawed as evidenced by the Attorney General’s legal advice."

Leading Tory rebel Steve Baker, the former Brexit minister, said: "Giving Parliament the choice between the devil and the deep blue sea is desperate and will persuade very few."

Asked why only 30 ministers were going about the country given the importance of the PM’s Brexit plan, her spokesman said: “Look, you have seen ministers engaging over the course of the last two weeks and I’m sure they will continue doing so in the final days ahead of the vote as well.”

Asked if the ministers travelling today had volunteered or were conscripted for the task, he replied: “We don’t so conscription in this country.”

Asked why the PM was not out and about selling her plan, her spokesman stressed how she had already been across the country talking to people about it and this weekend had constituency agreements.

Writing on Facebook, Mr Johnson said that the backstop "hands the EU the indefinite power to bully and blackmail this country to get whatever it wants in the future negotiations", because it denied the UK the power to leave without agreement from Brussels.

Predicting that France would use this advantage to "plunder" UK fishing waters, Spain would "make another push for Gibraltar" and Germany would demand concessions on migration, the former Foreign Secretary said: "It is quite incredible that any government could agree to such terms.

"They resemble the kind of diktat that might be imposed on a nation that has suffered a military defeat," he declared.

Meanwhile, Matt Hancock , the UK Health Secretary, confirmed that planes could be used to fly in drugs and medicines could be given priority access through gridlocked ports in the event of a no-deal Brexit.

"If there is serious disruption at the border we will have prioritisation, and prioritisation will include medicines and medical devices," he told BBC Radio 4's Today programme.

The Government, he explained, was also "buying a large collection of refrigeration units so that those drugs that can be stockpiled, we will have a stockpile of".

Elsewhere, Jeremy Hunt warned of "real social instability" if a second referendum resulted in a victory for Remain.

"For me as someone who voted Remain, my view is we will not have social stability in this country if we end with a solution that doesn't mean that we have parliamentary control of immigration policy," the Foreign Secretary told The Times Red Box.

If a fresh poll reversed the 52 per cent to 48 per cent majority for Leave in 2016, Leave supporters "would be incredibly angry and I wouldn't rule out real social instability in this country", said Mr Hunt.

In a newspaper article, Jeremy Corbyn repeated that "all options" - including a second referendum - must be on the table if Mrs May went down to defeat next week.

Writing in The Guardian, the Labour leader made clear that his preferred result remains a general election which might allow Labour to try to secure a Brexit involving a customs union which gave the UK a say in future EU trade deals, as well as a new single market deal allowing Britain control over migration and state aid.

"In the past, a defeat of such seriousness as May now faces would have meant an automatic election," wrote Mr Corbyn.

"But if under the current rules we cannot get an election, all options must be on the table. Those should include Labour's alternative and, as our conference decided in September, the option of campaigning for a public vote to break the deadlock."

Brandon Lewis, the Tory Chairman, said it was "the strongest signal yet that Labour are considering backing a second referendum, breaking his promise to respect the country's decision to leave".

He added: "All Jeremy Corbyn offers is more division and uncertainty. After nearly two years of long and complex negotiations, he would take us back to square one."