Prime Minister Theresa May asked EU leaders Wednesday for a three-month delay to Brexit amid continued political deadlock in London, but Brussels warned the postponement carried "serious legal and political risks."

Exactly 1,000 days on from Britain's seismic 2016 referendum vote to leave the European Union and with just nine days left until the scheduled departure date, the divorce deal is blocked in parliament and political turmoil grips the country.

Faced with the potentially catastrophic impact of Britain leaving its biggest trading partner with no deal on March 29, May said she would try one last time to pass her deal next week. If it passes, it would still need to be ratified, and she told MPs she has written to EU President Donald Tusk asking to push Brexit back until June 30. If she fails a third time, May said parliament would have to decide what happened next, but said she viewed any longer extension as "a failure to deliver on the referendum decision." She hinted that her own future was on the line, saying: "As prime minister, I am not prepared to delay Brexit any further than June 30." And the prospect of Britain having to hold European Parliament elections at the end of May would be "unacceptable," she said.

EU states which were due to receive additional legislative seats after Brexit would need to know by mid- to late April if they would be denied those seats because Britain was staying.

The European Commission argued that any Brexit delay beyond May 23, the day when Europeans start going to the polls, would require Britain to participate.

In a phone call yesterday, commission President Jean-Claude Juncker "clearly warned the prime minister" against an extension date after the EU elections, his spokesman Margaritis Schinas said. "He repeated in this call his advice ... that the withdrawal has to be complete before May 23 otherwise we risk facing institutional difficulties and legal uncertainty," Schinas added.

Spain's foreign minister said yesterday an agreement by the European Union to extend Brexit may only happen next week, just before March 29, when Britain is due to leave the bloc. "You know in Europe we always get a solution at the last minute," Foreign Minister Josep Borrell told Reuters, adding there "will be another occasion next week for taking the definitive solution." Borrell said the outcome will depend on what British Prime Minister Theresa May tells a summit of European leaders today. "Maybe [today] is not going to be enough and we have to jump over ... to just before the deadline," he said.