Article 50 can be extended until May 22 but only if MPs approve the deal. If they don't, the UK has until April 12 to come up with a plan or crash out without a deal.
A leaked European Commission memo seen by BuzzFeed News also cast doubts on May's plan for an Article 50 extension until June 30.
Brexit will be delayed until June 30 if MPs can agree a deal by the end of March, or potentially for much longer if they can't.
The prime minister suffered two more humiliating defeats in the House of Commons, but no-deal remains the legal default option until Parliament backs an alternative.
The EU Is Telling European Leaders There Are Only Three Reasons They Should Allow Brexit To Be Delayed
BuzzFeed News has seen a memo laying out the thinking at the highest level of the European Commission, and interviewed multiple officials and diplomats about extending Article 50.
MPs voted 391-242 against the prime minister's new deal, a margin of 149.
"The legal risk remains unchanged," Geoffrey Cox concluded in his legal advice published on Tuesday morning, just hours after Theresa May claimed to have resolved the issue.
EU Officials Say Theresa May Will Lose Credibility If She Asks MPs To Vote On Ideas The EU Has Already Rejected
“[May] will lose more credibility by playing this game,” an EU27 leader told BuzzFeed News.
The UK is trying to find a “legal solution to a political problem,” according to an EU27 diplomatic note seen by BuzzFeed News.
The prime minister informed the European Council president last Sunday, according to an EU27 diplomatic note seen by BuzzFeed News.
“There’s no chance of a ‘deal in the desert.’ It’s rather a ‘mirage’ or [a] ‘hallucination,’” an EU source told BuzzFeed News.
BuzzFeed News had earlier revealed the planned participation of Vladimir Yakunin, who is the target of US sanctions.
A Company Whose Director Represents Joseph Mifsud Changed Its Name To “No Vichok Ltd” After The Salisbury Attack
A Novichok nerve agent was identified as being used to poison Russian double agent Sergei Skripal and his daughter. One person later died as a result of the attack.
Exclusive: A diplomatic note seen by BuzzFeed News reveals that senior European diplomats think the prime minister is trying to “buy time” with MPs – and the risks of a “no deal by accident” are increasing.
Donald Tusk Told Theresa May That Jeremy Corbyn's Plan Could Be "A Promising Way" Out Of The Brexit Impasse
“Tusk suggested that the Corbyn plan could be a promising way out of the impasse.”
This Leaked Report Reveals The “Technological Solutions” Explored By Liam Fox To Keep The Border In Ireland Open After Brexit
The Irish government and the EU weren’t impressed.
Parliament has voted to send Theresa May back to Brussels for new talks about the hated Northern Ireland backstop. Within minutes, European leaders flatly rejected the idea.
Downing Street is looking at a "sunset clause" to add an end date to the controversial Irish backstop.
The EU Thinks Theresa May’s Attempts To Build Support With MPs For Her Brexit Deal Are Too Late And Will Probably Fail
A diplomatic note seen by BuzzFeed News also warns that extending Article 50 to delay Brexit would not be as simple as some people assume.
The government was defeated by 432 to 202, a margin of 230.