Boris Johnson has confirmed to European Council president Donald Tusk that he will be writing to him on Saturday night to seek a Brexit delay, the PA news agency understands.
The move comes after a defiant Prime Minister told the Commons he will not negotiate a fresh Brexit extension with the EU despite suffering an embarrassing defeat in Parliament.
At a special Saturday sitting, MPs voted by 322 to 306 in favour of an amendment withholding approval of his Brexit deal until legislation to implement it is in place.
The amendment tabled by former Cabinet minister Sir Oliver Letwin was intended to force him to comply with the so-called Benn Act requiring him to seek a Brexit extension.
The development came as the PM wrote to all Tory MPs and peers insisting that he will tell Brussels a further Brexit delay is “not a solution” to the situation.
In a letter to members of the Tory parliamentary party, the PM said: “I will tell the European Union what I have told the British public for my 88 days as Prime Minister: further delay is not a solution.”
He added: “It is quite possible that our friends in the European Union will reject Parliament’s request for a further delay (or not take a decision quickly).”
The PM also discussed the situation with French President Emmanuel Macron on Saturday.
Mr Tusk tweeted: “Waiting for the letter. I just talked to PM @BorisJohnson about the situation after the vote in the House of Commons.”
Amid noisy Commons scenes, Mr Johnson insisted that he was not “daunted or dismayed” by the vote result and remained committed to taking Britain out by October 31.
“I will not negotiate a delay with the EU, neither does the law compel me to do so,” he said.
Asked if previous statements from ministers that the Government would comply with the law still stood, the Prime Minister’s official spokesman told a Westminster briefing: “Governments comply with the law.”
Labour leader Jeremy Corbyn warned Mr Johnson that he could not ignore the provisions of the Benn Act.
“It’s an emphatic decision by this House that has declined to back the Prime Minister’s deal today and clearly voted to stop a no-deal crash-out from the European Union,” he said.
“The Prime Minister must now comply with the law. He can no longer use the threat of a no-deal crash-out to blackmail members to support his sell-out deal.”
The SNP leader at Westminster Ian Blackford said that if Mr Johnson acted as if we was “above the law”, he would find himself in court.
Liberal Democrat leader Jo Swinson said: “The most urgent thing right now is the Prime Minister complies with the law.”
The European Commissions’ chief spokeswoman Mina Andreeva urged the Government “to inform us about the next steps as soon as possible”.
The Benn Act sets a deadline of 11pm on Saturday for the Prime Minister to get a deal if the UK is to leave on October 31, otherwise he is supposed to seek an extension.
Commons Leader Jacob Rees-Mogg said the Government was planning to give MPs a fresh chance to have a “meaningful vote” on the deal hammered out by Mr Johnson with Brussels on Monday.
Speaker John Bercow said he would rule on Monday whether it was in order for the Government to hold the vote after not pressing ahead with it on Saturday following its defeat on the Letwin amendment.
SNP MP Joanna Cherry, who brought the case which led to Mr Johnson’s suspension of Parliament being ruled unlawful, said they would continue to pursue the Prime Minister through the court to enforce the Benn Act.
“We’re back in court on Monday morning and it will be possible then to secure the court’s assistance if the Prime Minister has flouted the law and the promises he gave to the court,” she told the Commons.
The voting took place as tens of thousands of protesters converged on central London in a People’s Vote campaign march in support of a second referendum.
The result was greeted by loud cheers by the crowd assembled outside the Palace of Westminster in Parliament Square.
The Government was consigned to defeat after the 10 MPs of Mr Johnson’s erstwhile allies in the DUP joined the other opposition parties in voting for the amendment.
The party is furious about the proposed customs arrangements for Northern Ireland which would see checks on goods coming from the rest of the UK.
Ten former Conservative MPs who now sit as independents, including former cabinet ministers Ken Clarke, Philip Hammond and Amber Rudd, also backed the amendment.
In contrast, just six Labour rebels voted against it.
Following the vote, Mr Johnson said that he did not believe the other EU member states would be “attracted” to a further delay.
He said the Government would be tabling legislation next week to implement the terms of the agreement.
“I hope that then Honourable Members, faced with a choice of our new deal for the UK and the European Union, will change their minds because it was pretty close today,” he said.
“I hope that they will change their minds and support this deal in overwhelming numbers.
“I will continue to do all I can to get Brexit done on October 31.”