Boris Johnson has sent a request to the EU for a delay to Brexit – but without his signature.
The request was accompanied by a second letter, signed by Mr Johnson, which says he believes that a delay would be a mistake.
The PM was required by law to ask the EU for an extension to the 31 October deadline after losing a Commons vote.
EU Council President Donald Tusk tweeted that he had received the extension request.
He added he would now consult EU leaders “on how to react”.
Hours after losing a crunch vote in a historic Saturday session in the House of Commons, the prime minister ordered a senior diplomat to send an unsigned photocopy of the request for a delay, which was forced on him by MPs last month.
The second letter from Mr Johnson – signed off this time – makes clear he personally believes a delay would be a mistake.
It says the government will press on with efforts to pass the revised Brexit deal agreed with EU leaders last week into law, and that he is confident of doing so by 31 October.
A cover note from Sir Tim Barrow, the UK’s representative in Brussels, explained the first letter complied with the law as agreed by Parliament.
The prime minister previously said he would “rather be dead in a ditch” than ask the EU to delay Brexit.
BBC Political Editor Laura Kuenssberg described the decision to send three documents as “controversial”, predicting “there will be a fight about whether Boris Johnson is trying to circumvent the court”.
She added: “This is heading straight for the court, and it may very quickly end up in the Supreme Court.”
Earlier, Mr Johnson rang European leaders, including Mr Tusk, to insist that the letter “is Parliament’s letter, not my letter”.
Extracts from Mr Johnson’s letter to Mr Tusk:
“The UK Permanent Representative will… submit the request mandated by the EU (Withdrawal) (No.2) Act 2019 later today. It is, of course, for the European Council to decide when to consider this request and whether to grant it.
“Although I would have preferred a different result today, the Government will press ahead with ratification and introduce the necessary legislation early next week. I remain confident that we will complete that process by 31 October.
“While it is open to the European Council to accede to the request mandated by Parliament or to offer an alternative extension period, I have made clear since becoming Prime Minister… that a further extension would damage the interests of the UK and our EU partners, and the relationship between us.
“We must bring this process to a conclusion so that we can move to the next phase and build our new relationship on the foundations of our long history as neighbours and friends in this continent.”
At the first Saturday sitting in the Commons for 37 years, MPs voted in favour of an amendment withholding approval of Mr Johnson’s Brexit deal until legislation to implement it is in place.
Tabled by Tory MP Sir Oliver Letwin, the amendment was intended to ensure that Mr Johnson would comply with the terms of the so-called Benn Act.
Under that Act, which required the PM to seek a Brexit extension, Mr Johnson had until 23:00 BST on Saturday to send a letter requesting an extension.
In a letter to MPs and peers on Saturday evening, he warned that the EU could reject “Parliament’s request for further delay” and added that he “will not negotiate a delay”.
“I will tell the EU what I have told the British public for my 88 days as prime minister: further delay is not a solution,” he said.
The Commons defeat marked a major setback for the PM, who has repeatedly insisted that the UK will leave at the end of the month come what may.
Mr Johnson told the Commons that he was not “daunted or dismayed” by the defeat and remained committed to taking Britain out by the end of the month on the basis of his “excellent deal”.
An EU source said that once Mr Tusk received the letter, he would start consulting EU leaders on how to react – which may take a few days, BBC Brussels reporter Adam Fleming reported.
Mr Johnson has vowed to bring in legislation on Monday to implement the deal he struck with Brussels this week.
MPs could also be given another vote on the deal then, if Commons Speaker John Bercow allowed it.
Boris Johnson literally spelling out his opposition to prolonging the Brexit process by writing a separate letter to Brussels to say so, makes it easier for his peers Emmanuel Macron, Angela Merkel and others to drag their feet a little.
They prefer first to look to the prime minister to make good on his promise to them that their newly-negotiated Brexit deal will *definitely* be passed by Parliament.
But, if push comes to shove, with the alternative being no deal at all… I cannot imagine the EU slamming the door in the face of the UK now.
They will want to know what [the extension] is for. Are there plans in the UK to hold a general election, a second referendum or a referendum on the new Brexit deal? Or is a bit more time needed to pass Brexit-related legislation?