Theresa May has told her cabinet she is ready to reopen negotiations with the EU on the Brexit Withdrawal Agreement to secure changes to the controversial backstop plan to avoid a hard border in Ireland.

The Prime Minister said that, following this month's crushing 230-vote defeat in the Commons, it was clear that only reopening the agreement and changing the backstop will win MPs' support for her EU withdrawal deal.

In a change to previously announced plans, she will address MPs at the start of debate on a series of proposed amendments to the deal, urging them to back proposals from Tory grandee Sir Graham Brady to replace the backstop with "alternative arrangements".

In an apparent attempt to fend off possible defeat on other amendments which could delay Brexit or rule out a no-deal departure, Mrs May promised that Tuesday's votes would not be MPs' final chance to pass judgment on EU withdrawal.

Her hopes of victory for the Brady amendment were boosted when former foreign secretary and Brexit figurehead Boris Johnson said he would "gladly" vote for it - if it meant the Withdrawal Agreement being reopened and legally binding changes being made to the backstop.

First Minister Nicola Sturgeon said the Prime Minister's new position was "undeliverable" and "highly irresponsible".

She tweeted: "PM surely can't be allowed to continue down a track that might avoid defeat at hands of ERG today but is ultimately doomed to failure - and which therefore increases the chance of no deal.

"It is highly irresponsible."

Responding to speculation May could win a majority around the Brady amendment, Sturgeon added sarcastically: "A majority for an undeliverable position. Bravo."

But the chances of the Commons derailing May's plans were also heightened when Labour confirmed it will back a cross-party amendment to push Brexit day back from March 29 to the end of this year and put Parliament in the driving seat on the way forward.

This proposal, tabled by Labour's Yvette Cooper and Tory Nick Boles, is one of the strongest-backed of a bevy of rival amendments tabled for debate. Only those selected by Speaker John Bercow will go forward to a vote.

Mrs May is expected to have phone discussions with key EU leaders over the course of the day, with votes taking place in the early evening.

Speaking to Cabinet, she said she aims to return to the Commons "as soon as possible" with a revised deal, which will be subject to a "meaningful vote" of MPs. If it is defeated, she will table another amendable motion for debate the following day.

If no new deal is reached by February 13, the PM will make a statement to Parliament that day and table an amendable motion for debate the following day.

Her announcement brought the prospect of the cancellation of Parliament's half-term recess a step closer, as the Commons is currently due to rise for its 10-day break on February 14.