The prime minister has requested a further extension to the Article 50 negotiating period to 31 January 2020.
Boris Johnson has asked the EU for a three-month delay to Brexit, which would extend the Article 50 negotiating period to 31 January 2020.
The request to European Council President Donald Tusk was made in an unsigned letter late on Saturday night.
It came hours after MPs voted to withhold their approval for Mr Johnson's Brexit deal unless and until he has passed all necessary legislation to implement it.
The prime minister was legally required to request this delay under the so-called "Benn Act". The legislation was passed by opposition MPs in September to prevent a no-deal Brexit at the end of this month.
On Twitter, Mr Tusk said: "The extension request has just arrived. I will now start consulting EU leaders on how to react."
Mr Johnson - who has previously said he would rather die in a ditch than delay Brexit again - has rung European leaders to distance himself from the request, describing it as "parliament's letter, not my letter".
The PM has also sent a separate note to Mr Tusk, obtained by Sky News, in which he urged the EU not to grant the extension.