Theresa May has written to European Council President Donald Tusk to formally request a short, one-off delay to Brexit beyond 29 March.
The prime minister told MPs she was "not prepared to delay Brexit any further than the 30 June".
During a fractious PMQs, she said MPs had "indulged themselves on Europe for too long" and she wanted to avoid the UK taking part in European elections.
Labour leader Jeremy Corbyn accused her of leading the UK into "crisis".
"We are still legally due to leave the European Union in nine days' time," he told the PM.
"Months of running down the clock and a concerted campaign of blackmail, bullying and bribery has failed to convince the House or the country that her deal is anything but a damaging national failure and should be rejected."
The European Commission is telling EU leaders that the UK must take part in elections for the European Parliament if it stays in the EU beyond the 23 May.
In a document seen by the BBC, the Commission says: "Any extension offered to the United Kingdom should either last until 23 May 2019 or should be significantly longer and require European elections.
"This is the only way of protecting the functioning of the EU institutions and their ability to take decisions."
Any delay to Brexit must be agreed by all 27 member states.
Source: BBC