British Prime Minister Theresa May has received an endorsement of her Brexit deal from the Conservatives’ backbench leader, who said he will recommend that Members of Parliament support it – if the prime minister secures new assurances on the Irish backstop.

May’s hopes of winning parliamentary approval for her Brexit deal grew as Graham Brady, the powerful chairman of the 1922 Committee, said he is ready to drop his opposition to it.

The move is a significant shift and came as senior government sources predicted that May could hold the crucial meaningful vote as early as this week.

In an article written for the Mail on Sunday newspaper, Brady condemned the government's handling of the Brexit negotiations as “lions led by donkeys”.

He said: “The whole country is tired of vacillation and delay.

“When the right compromise is offered, we should pull together behind the prime minister and help her to deliver our exit from the European Union on March 29.”

Only weeks ago Brady pushed through an amendment that instructed May to return to Brussels to negotiate the complete removal of the backstop from the withdrawal agreement.

The Brady amendment, which passed through the Commons by 318 votes to 310 on Jan 29, called for “the Northern Ireland backstop to be replaced with alternative arrangements to avoid a hard border” and said a deal on leaving the EU would be dependent on its being removed.

In his article, Brady added: “In the month since my amendment was passed, there has been constant shuttle diplomacy – the prime minister, Brexit secretary, and attorney general have been locked in daily discussions to find the binding guarantee that is needed.

“My conversations with senior diplomats and politicians from across Europe have given me cause for optimism that a breakthrough is near.

"Those who have pressed for delay or for no deal to be taken off the table have weakened Theresa May's hand and made a deal less likely, but I still believe a compromise is fundamentally in our interest and that of the EU.

"We know what is needed to shift the logjam. The attorney general needs to give a legally binding guarantee that the backstop is temporary.

“Once we have that, my colleagues in Parliament need to recognize the strength of feeling.”

Meanwhile, according to the Sunday Times, the Brexit-backing European Research Group – a Eurosceptic faction of the Conservative Party– has set out its demands May must meet to secure its support for her deal with the EU.

They still want a time-limit to the Irish backstop – but they say they don't mind how that is achieved. They had previously been demanding specific legal changes to the agreement.

The move by the ERG is seen as a softening of its previous stance on the backstop, which is meant to guarantee the return of a hard border on the island of Ireland.

May has promised MPs a vote on her deal on or before March 12. The UK is due to leave the EU on March 29, with or without a deal.