THERESA May is asking her party to support a backbench amendment to the Brexit deal that calls for the planned Irish backstop to be replaced with “alternative arrangements”.

While senior figures in Brussels are opposed to changing the backstop, Graham Brady has suggested a legally binding “codicil” – an annexe setting out the determination of both sides that the backstop must be temporary – would suffice.

Tory MPs will be told to vote for the Brady amendment when the Commons votes to unlock a stalemate over the Prime Minister’s withdrawal agreement which was defeated by 432 votes to 202 earlier this month.

A range of other amendments to her deal have been put down – including delaying the UK’s departure from the EU on 29 March, blocking a no deal, and demanding a softer Brexit.

However, there is concern none will get a Commons majority and that the impasse will continue.

A second “meaningful vote” on the deal is due to take place next month.

Last night reports emerged members of the European Research Group of Eurosceptics were unlikely to back the Brady amendment as for them it did not go far enough to drop the backstop.

Former chancellor George Osborne, meanwhile, suggested Brady “was chasing unicorns” as his amendment was “a fantasy” which the EU would never agree to.

Writing in the Evening Standard, he said: “Tory backbench chief Sir Graham Brady has put down a motion that in effect says he and other rebels would happily back Theresa May’s deal, if only she can get the EU to drop the Irish backstop, which she negotiated with them.

“He says passing the amendment would give the PM ‘enormous firepower’ to force Europe to back down.

“But there is no prospect of Brussels or Dublin doing that. They said so again yesterday.

“The Irish backstop is the only solution the British and European negotiators found, after two years of intensive talks, to square the Prime Minister’s foolish red lines of leaving the customs union, while keeping the Irish border open and maintaining the integrity of the UK.

“Just because Brexiteers think there’s a unicorn to be discovered out there in the forest does not mean anyone else has to indulge their fantasies.”

Meanwhile, May received more setbacks from senior figures in Brussels yesterday.

Sabine Weyand, the European Commission’s deputy chief negotiator, insisted there would be no further talks with the UK over the EU withdrawal agreement and warned there was now “a very high risk” of an no deal outcome.

“There’s no negotiation between the UK and EU – that’s finished,” she told an event held by a think tank in the Belgium capital.

“We’re not going to reopen the agreement. The result of the negotiation has been very much shaped by the UK negotiators, much more than they actually get credit for.

“This is a bit like snatching defeat from the jaws of victory. The backstop was very much shaped by UK.”

Speaking at a panel discussion organised by the European Policy Centre, she went on: “There’s a very high risk of a crash out not by design, but by accident.”

Earlier European Commission spokesman Margaritis Schinas also insisted Brussels would not reopen the talks.

“We have a unanimous EU27 position on the withdrawal agreement which reflects the common EU position,” he said.

“This withdrawal agreement has been agreed with the UK Government, it is endorsed by leaders and is not open for renegotiation.”

Asked if that position would change if MPs vote to demand changes to the Irish backstop, Schinas said: “The only thing I have to say is that we shall wait for the result of the vote of the Commons tomorrow.

“Then we will wait for the Government to tell us what are the next steps.

“That’s how it’s going to work,” she added.