Theresa May called an early election for June
Mrs May needs a two-thirds majority in the Commons in order to bypass the Fixed Term Parliaments Act, with a vast number of Labour MPs expected to vote in favour of the motion.
She will need 434 votes – 104 more than the current number of Conservatives in Parliament – thus requiring Labour backing.
In December 2016, Labour leader Jeremy Corbyn said that he would instruct his MPs to back a snap election if a vote was called.
He said: "If there’s a vote to dissolve Parliament then obviously we will vote with it.”
The Fixed Term Parliament Act was brought in after the 2010 Coalition government was formed.
It is due to this that the Prime Minister must win the backing of MPs in order to bring the election forward from 2020.
If the Prime Minister failed to secure the necessary number of votes to bypass the Act, she may be forced into a vote of no confidence in her own government.
If no confidence was declared, other parties would be given a 14-day period in which to form a new government.
THIS IS A LIVE STORY – REFRESH FOR UPDATES
THE DEBATE HAS COME TO AN END – MPs ARE NOW VOTING.
A reminder that the SNP has said it will abstain – however with around 330 Conservatives and most Labour MPs, the threshold is likely to be easily met.
The number of No or Abstained votes don't actually matter in this particular poll – it's just the Yes votes that count.
2.30PM BST: SNP MP Alan Brown stands up in the Commons to ask what Theresa May will do to stop Conservative MPs “cheating” with their spending this time around.”
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That irks Tory MP Anne Main, who intervenes to say: “Twice the honourable member has accused members of cheating. There is no proof of cheating and he should withdraw the remark.”
Speaker John Bercow says it is a question of taste rather than rules in the House.
2.25pm BST: The SNP's Tommy Sheppard complains that the call for an early election is "a blatant abuse of parliamentary procedure for party political gain”, adding that an “authoritarian" Prime Minister wants to "silence dissent".
2.20pm BST: Labour veteran Dennis Skinner turns to the history books to warn against making this an election based around Brexit.
"“The nearest parallel is the election of 1974 when Ted Heath, the then PM decided on a very narrow argument: that the miners were on strike and it would be about who rules the country. Most eletions are about a lot of things; this one was about a specific thing.
"Can I say to my Honorable Friend that what happened in respect is the Labour party finished up with the largest number of seats”.
2.05pm BST: Labour's David Winnick is unimpressed by the Prime Minister's move.
The veteran MP says: "This motion that is before is murky, completely opportunist and certainly it reflects badly on the Prime Minister.
"This motion and this general election which is coming – purely for opportunistic reasons – will increase that cynical feeling and that is very damaging indeed to the democratic process."
2pm BST: Tory politician Jacon Rees-Mogg says the Fixed Term Parliament Act isn't working and "has to go”.
The DUP's Nigel Dodds says this snap election is an opportunity to reject Sinn Fein's "Marxist-Leninist" republicanism and protect the Union.
Plaid Cymru’s Hywel Williams takes aim at Theresa May’s U-turn on an election: "The record is about as straight as the legendary European Union banana."
1.50pm BST: SNP MPs are challenging Farron to rule out a coalition with the Tories – the Lib Dem leader ducks the question.
Tim Farron is asked by Tory MP Nigel Evans whether he believes being homosexual is a sin.
Mr Farron responds: "I do not."
The Lib Dem leader had dodged the question when quizzed on Channel 4 last night.
1.45pm BST: Lib Dem leader Tim Farron is up in the Commons now, and he takes a swipe at former PM David Cameron.
“Given that we are in this mess in one sense as a country because he put party before country when he did, it is hardly surprising that the Prime Minister should follow him and indeed put party before country once again.”
Mr Farron says Theresa May was unable to resist “doing the political equivalent of taking candy from a baby” and calling an election against the Labour party.
He goes on to say that the Prime Minister "expects a coronation, not a contest. There is only one route to the PM losing this election, and it is a Liberal Democrat route."
1.40pm BST: Deputy SNP leader Angus Robertson is up. Playing the 'Tories v SNP' narrative, he says: “While she thinks that she can get away with all of this against the Labour party in England, she will not get away with this in Scotland.”
Mr Robertson returns to the burning question of the PM's refusal to participate in TV debates. He says it's "unsustainable" in the 21st century digital era that a Prime Minister could be "empty chaired".
Tory MP Nigel Evans repeats his support for the PM saying: “I hope that the PM does go head to head with the leaders of the other parties. It’s quite simple, Mr Speaker, she would floor them all.”
Mr Robertson concludes by looking forward to the SNP vs Conservative fight in Scotland – his colleagues give him a round of applause.
SNP MPs are expected to abstain this afternoon – this move will amount to a vote against.
1.30pm BST: Former Tory minister Sir Desmond Swayne is the first backbencher up. He says that the PM has, for a second time, committed a u-turn on something he has just defended in the Forest Journal. He's been making the case to his constituents that an early election would not be happening.
He then congratulates Labour benches on being "turkeys voting for Christmas" – almost daring Labour not to back the motion.
In a colourful contribution, Mr Swayne says he has undergone a conversion since backing all of Theresa May's competitors for the Conservative leadership.
“I have become her greatest fan and, as my constituents recognise and tell me continually, she is doing magnificently and may she long continue to do so.”
PMQs live images Wed, April 19, 2017
Theresa May arrived in the Commons for PMQs to a roar of applause from her Conservative colleagues
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'Labour party will be going into the election pledging to spend £5billion extra’
1.25pm BST: The Labour leader targets Conservative MPs facing expenses charges, questioning the Prime Minister if her real intention behind an early election is down to fears of losing backbenchers due to the election expenses investigation.
He points out that the PM has failed to mention it.
Mr Corbyn accuses the Prime Minister of paining herself as a "prisoner of the Lib Dems.
"There are nine of them and they managed to vote three ways on Article 50 so it’s obviously a very serious threat indeed."
1.15pm BST: Jeremy Corbyn step up: "We welcome opportunity of general election"
Corbyn reminds MPs that only four weeks since PM spokesman said there would be no election. "How can people trust what the PM says?"
He says this is a change for the country to "change direction" and says it's about the crisis the NHS is in and the cuts to school funding.
Mr Corbyn faces heckling and is forced to give way to Labour's Gareth Snell.
Mr Snell says the PM's call for election shows she has no confidence in herself to get the job done.
Corbyn thanks him for his intervention.
1.10pm BST: May: "General Election wll provide the country with five years of stable leadership"
The Prime Minister says this provides time and a mandate for longer negotiations – allowing adequate time for transition and implementation.
Speaking to the Opposition, she goes on to say that "anyone who abstains in this vote is presumably endorsing the record of a Conservative government."
A reminder that the Prime Minister needs 434 positive votes in favour of a snap election under section 2 of the Fixed Term Parliament Act.
1pm BST: The debate kicks off with Theresa May taking questions saying: "Yesterday I've gave the country a very clear indication of my intentions.
"I believe its in Britains national interest to hold an election now" says PM in opening snap election debate
"Now is the time for a General Election because it will strengthen our hands in negotiation. A Scottish referendum will weaken our hands.
"I believe at this moment of national significance, there should be unity not division."