British Prime Minister Theresa May has warned her Tory opponents that their alternate Brexit plans would not make their problems disappear as she faced a continuing battle to win over sceptical MPs.

After bolstering her Cabinet by bringing back former home secretary Amber Rudd, Mrs May warned that the so-called Norway and Canada models favoured by her most hardline critics would not solve the issue of the Irish border backstop.

The comments come after a tumultuous week that saw the departure of ministers from Mrs May’s cabinet including Brexit secretary Dominic Raab and work and pensions secretary Esther McVey.

Ms Rudd pleaded with Tory rebels to back the Prime Minister and her Brexit deal on her return to Government as the new Work and Pensions Secretary, saying: "This is not a time for changing our leader."

Amber Rudd returns to government as Work and Pensions Secretary

But the Prime Minister's critics believe they have the numbers required to trigger a confidence vote within days.

Five Brexit-supporting ministers led by Andrea Leadsom are reportedly set to work together on measures to make the deal more acceptable to them.

The Brexiteer Commons leader Andrea Leadsom said there is still time for "more to be done" on the Brexit deal.

She said she supports the Prime Minister but suggested there is an opportunity before a special European Council meeting on 25 November to get "the best possible deal for the UK".

Andrea Leadsom says more can be done on the Brexit deal

Her comments came after Brexiteers vying to oust Mrs May were warned their efforts could drive Remain-voting Tories to attempt to stop Brexit entirely.

In a sign the Tory civil war over Brexit is not slowing down, Middle East Minister Alistair Burt warned rebels the "consensus" that pro-EU MPs should reluctantly respect the 2016 referendum result could break down if she is toppled.

Meanwhile, the Shadow chancellor John McDonnell has suggested that Labour could negotiate Theresa May's withdrawal agreement before Britain is due to leave the European Union, despite that happening in four-and-a-half months time.

He told Sky News that there was support in Parliament and in Europe for a "unity platform" that avoided a no-deal Brexit when the UK leaves in March.

Asked if he would extend Article 50 to give politicians more time to seek a different agreement, he said: "I believe we can do it within the (current) timescale itself.

"It is tight and I accept that, and that is the frustration, that we have got right the way across the House of Commons, the frustration of why has the last two years have been wasted in the way it has, in the internal disputes within the Conservative Party, when there should have been these negotiations.

"I think we can do it with good will, we can change the atmosphere of negotiations into one of mutual interest and mutual benefit, and on that basis I think we can have a constructive negotiation rather than the dreadful way in which the government has negotiated over the last two years."

Earlier, the Scottish Secretary David Mundell pledged his support for Theresa May amid what he called an "unprecedented onslaught" by her critics.

Mr Mundell said he has reservations about the Prime Minister's draft Brexit deal but other alternatives were "even more unpalatable".

He told a gathering of Scottish Conservatives in Falkirk that he would continue to press for reassurances the UK would leave the EU Common Fisheries Policy in December 2020.

Mr Mundell said: "She is tackling an issue of epic proportions, on which she can never please everyone, and she is doing her very best to find a way through.

"Let me be quite clear, if it comes to a confidence vote, she will have mine."