Brexit minister Kwasi Kwarteng, who is backing Theresa May, tells 5 live he is confident she will win and hopes she will "win decisively".

He believes that the "mood has swung in her favour" during the course of the day.

While he accepts many Brexiteers are frustrated, he says the PM has listened to the concerns of MPs about the EU withdrawal agreement and the vote is a distraction.

Asked about whether he supports the PM leading his party into the next election, scheduled for 2022, he says he won't speculate on what might happen in more than three years' time.

Professor John Curtice, from the University of Strathclyde, says: "The bigger the vote against the prime minister, the more emboldened will be those minded to vote against her deal.

"If she has got over 200 votes, that can be regarded as a reasonable outcome.

"If much more than 100 Tory MPs vote against her she is going to be struggling to remain in her position for very long.

"100 MPs voting against her would imply that either ministers had voted against her or a majority of Conservative backbenchers have voted against her."

Image source, PA

If Theresa May fails to get a majority in the secret ballot there will be a leadership race to replace her.

Here - based on the latest odds at the bookmakers - are the fancied runners.

None have so far declared their intention to stand.

BBC News

BBC political correspondent Ben Wright says Brexiteers seem "flatter" than Theresa May's supporters.

However, he adds that one cabinet minister has described Conservative MPs as "the most duplicitous electorate in the world - you can never tell who is lying".

Our correspondent says that "while there is confidence that she has got the numbers, nobody is being complacent.

"A lot could change. A lot is riding on how the prime minister performs at the 1922 committee at 17:00 GMT."

Image source, Reuters

2003

Iain Duncan Smith, who was Tory leader but not prime minister, faced a vote on his leadership barely two years after taking over from William Hague.

The Conservatives had just 165 MPs at the time, during Tony Blair’s second term as PM, and he lost by 90 votes to 75.

Michael Howard won a one-horse race to become the next leader.

1990

Prime Minister Margaret Thatcher was challenged by Lord Heseltine for the leadership in November 1990 – under old party rules a leader could only be challenged by someone standing against them.

Mrs Thatcher received 204 of the votes, compared to 152 for Mr Heseltine – 16 MPs abstained.

The result left the prime minister four votes short of the 56 majority required.

She resigned as leader two days later after advice from her cabinet, bringing to an end her more than 11 years as prime minister.

BBC News

Chief Secretary to the Treasury Liz Truss says now would be "a completely crazy time" to have a leadership election.

The prime minister has a clear plan and is getting the extra agreements she needs from her European leaders to satisfy Conservative MPs, she says.

She compares going through a leadership election to throwing dice in the air.

It may not be until 21:00 GMT that we find out the numbers, but the different factions of the Conservative Party and the opposition are already trying to put their spin on any outcome.

See this tweet from Politico's chief UK correspondent...

Andrew Griffiths has had the Conservative whip restored and will be voting for Theresa May in the no confidence vote.

The former small business minister resigned in July after a newspaper reported how he sent hundreds of lewd text messages to two women, and he was then suspended by the party.

The Staffordshire MP said in a statement: “Theresa May has shown huge determination and bravery in negotiating and arguing for her deal.

"I believe she remains the best person to deliver the Brexit people in Burton and Uttoxeter voted for, and I will be supporting her in tonight’s ballot."

It now means 316 MPs can take part in the ballot, and so the PM will need 159 for a majority.

Image source, UK Parliament

BBC Radio 5 live

Work and Pensions Secretary Amber Rudd tells BBC Radio 5 live she hopes colleagues will consider the risky alternatives to Theresa May's approach.

"Today will have been important for them to realise that they can’t change leader, and so we have a prime minister, we have a deal," she says.

She says the alternatives are more "uncertainty" and "volatility".

"We are under a ticking time bomb in a way. We are leaving the European Union at the end of March, we have a deal on the table. Anything could happen if this deal doesn’t get through."

Opposing Mrs May's withdrawal agreement could derail Brexit, lead to leaving the EU without a deal or trigger a general election and let the Labour Party in, she says.

But she denies that Mrs May's authority will be damaged by a close vote.

"You either win or you lose. I would rather she wins by a large amount but winning is the point."

She says she is campaigning for Mrs May and describes it as "a mistake, an indulgence" to speculate about whether she would stand if the no confidence vote is passed.

BBC Radio 5 live

Image source, Lucy

Lucy, 26, works in financial services and lives in Surrey: "This is a time of national crisis, it's not a time for a leadership contest... A new Conservative leader isn't going to make this whole mess and chaos go away, and it won't actually change the fundamentals of the negotiation.

"Theresa May is in a really difficult position. Brexit is a poisoned chalice and she's never going to please everyone."

Image source, Tom Willett

Tom Willett, 21, is in his final year studying politics at the University of Liverpool. He describes himself as a former Conservative, saying he'll support the party again if Theresa May goes:

"I think she will comfortably survive tonight but I think the problems come after. I expect her to get about 100 votes against her and once that happens her position becomes quite untenable.

"Remember all it takes is for Arlene Foster to pull DUP support and the government collapses."

Image source, Jack Powell

Jack Powell, 20, is the founder and editor of 1828, a youth-led political opinion website: "I think she has to go at this point. I think it's been a long time coming, I think this is a mess totally of her own creation. She may have worked tirelessly over the last two years, but what's she working for?

"If they don’t oust her, are they happy for her, in the next 12 months, to be untouchable, able to lead us into a general election?"

Image source, Stuart Collier-Daintith

Stuart Collier-Daintith, 27, lives in Manchester and is studying international relations and politics:

"It changes nothing whether she stays or whether she goes.

"If she stays then at least it provides some form of certainty and some sort of clarity.

"If you get Boris Johnson who advocates 'no deal', he said he can renegotiate and get rid of the backstop.

"There's no arithmetic in Parliament for any of it. I just don’t understand the point of getting rid of her now, when it's not going to change anything."

Click here to listen to full coverage on BBC Radio 5 Live.

BBC News

Jane Foley, a senior strategist at Rabobank, says a recovery for the Pound is down to suggestions that Theresa May may win the no confidence vote tonight.

"If that is the case that will remove one layer of uncertainty for the markets," she says.

"There is still a huge amount of uncertainty about Brexit. At least if Theresa May remains as prime minister that is one less thing for investors to worry about."

BBC News

The Institute for Government's Dr Catherine Haddon is answering questions from viewers on the BBC News Channel.

Dave Smethurst asks: "If Mrs May fails to win a no confidence vote will she stay on as prime minister or will her deputy step in?"

Dr Haddon says Theresa May can stay on as prime minister and points out that when David Cameron resigned in 2016 he still stayed in post until a new leader was elected.

Andrew and Pat Barnes ask whether the opposition can still table a motion of no confidence in the government if the PM wins the vote this evening.

The opposition can still put down a motion of no confidence and could trigger a process that leads to a general election, replies Dr Haddon.