MPs are set to vote today on Prime Minister Theresa May's call for a snap General Election.
The vote, which follows Mrs May's surprise decision to call for an early election despite repeatedly saying she had no intention of doing so, is required under the Fixed-term Parliaments Act.
Under the legislation two-thirds of the House of Commons - or 434 MPs - will need to support the proposal and agree to dissolve parliament, but with opposition parties backing the call it seems all but assured to pass.
Labour leader Jeremy Corbyn faced down calls from some MPs at a Westminster meeting on Tuesday evening for the party to abstain in the hope of forcing Mrs May to call a vote of no confidence in her own government.
Aides were unclear whether he will impose a three-line whip on MPs to vote in favour.
It seems likely that Britain will be heading to the polls on June 8, giving the election machine less than two months to put everything in place for polling day.
Overnight Mrs May spoke to US President Donald Trump who "wished the British people the best of luck in their electoral process", the White House said.
Mrs May's change of heart on an early general election has come about, she has suggested, in order to end "political game-playing" and strengthen her hand as she navigates Brexit.
In an exclusive interview with ITV News Political Editor Robert Peston the prime minister said she came to the conclusion an election was necessary shortly before Easter, while walking in Wales with her husband Philip.
Announcing the plan yesterday she said an early General Election was "the only way to guarantee certainty and security for years ahead".
But it is clear that in part Mrs May decision also arose from concerns that the 2020 election date, stipulated by the Fixed-Term Parliaments Act, would leave her facing an election vulnerably close to the end of the two-year EU withdrawal negotiations.
A fair wind in the expected June election could instead allow Mrs May to improve her slim 17-seat majority and push the next election date back to 2022, by which time the UK should have long ago left the EU.
Labour's Mr Corbyn said Mrs May's decision had given voters the chance "to vote for a government that will put the interests of the majority first".
While Liberal Democrat leader Tim Farron said the election provided an opportunity to block "a disastrous hard Brexit".
Scottish First Minister Nicola Sturgeon described the election call as "a huge political miscalculation by the prime minister" which would allow the SNP to reinforce its democratic mandate to stage a second referendum on independence.