Embattled British Prime Minister Theresa May may be facing a no-confidence motion after delaying a parliamentary vote on her Brexit deal, local media reported late Tuesday.

At least 48 of the 315 Conservative lawmakers in the parliament's 650-seat main elected house, the Commons, need to write to Conservative backbench 1922 Committee chairman Graham Brady to trigger the vote.

BBC political correspondent Laura Kuenssberg cited "multiple sources," including senior Conservatives and a cabinet minister, as saying that Brady had requested to see the prime minister after the weekly question time session on Wednesday.

"They believe the threshold of 48 letters has been reached," Kuenssberg tweeted.

Former Northern Ireland and environment secretary Owen Paterson is one of the lawmakers who expressed "no confidence" in the British leader, the Telegraph reported.

"The prime minister's proposed 'deal' is so bad that it cannot be considered anything other than a betrayal of clear manifesto promises," Paterson said in his letter to the chairman published by the Telegraph on Tuesday evening.

Downing Street could not immediately be reached for comment.

If enough letters were sent to trigger a vote, May would need the support of at least 158 of the 315 Conservative members of parliament to stay in office.

In case of a May victory, the 1922 Committee would not be able to call another no-confidence vote for a year, while if she lost she wouldn't be able to take part in the contest to choose a new Conservative leader.

The reports emerged after May crossed the English Channel on Tuesday in a last-minute bid to win concessions from European Union leaders.

Her trip to Berlin, The Hague and Brussels came on the heels of her decision to delay a planned vote on her deal in parliament after admitting she faced defeat "by a significant margin."

She is seeking reassurances that a so-called backstop agreement for the post-Brexit Irish border would not leave Britain trapped in an indefinite arrangement, an aspect of the agreement which has worried many lawmakers in Britain.

May is also set to travel to Dublin on Wednesday and to attend a summit of European leaders on Thursday.

There have been persistent reports that Conservatives were on the verge of triggering a no-confidence vote in May since she first agreed to the withdrawal deal, which spells out the legal terms of Britain's departure from the EU on March 29, 2019.