- Video report by ITV News Correspondent Angus Walker
Brexiteers Dominic Raab and Andrea Leadsom have formally launched their bids to take over from Theresa May as the next Conservative leader, as the war of words between candidates turns sour.
Former Brexit Secretary Raab, who resigned over Mrs May's Withdrawal Agreement, said he planned to "fight for a fairer deal on Brexit, a fairer deal for British workers and a fairer society where every child can fulfil their potential".
Writing in The Mail On Sunday, Mr Raab said he would prefer to leave with a deal but that the UK must "calmly demonstrate unflinching resolve to leave in October - at the latest".
He added: "The country now feels stuck in the mud, humiliated by Brussels and incapable of finding a way forward.
"The Prime Minister has announced her resignation. It's time for a new direction."
Meanwhile Ms Leadsom, writing in the Sunday Times, said she would be willing to walk away from the EU in October without a deal, stating: "To succeed in a negotiation you have to be prepared to walk away."
Ms Leadsom added that she would introduce a citizens' rights bill to resolve uncertainty facing EU nationals, then seek agreement in other areas where consensus already exists, such as on reciprocal healthcare and Gibraltar.
Raab and Leadsom's foray into the leadership battle comes as Jeremy Hunt put forward his own case to become the next leader in an article for the Sunday Times.
The Foreign Secretary said his business background would help him resolve the Brexit impasse.
Speaking to The Sunday Times, Mr Hunt said: "If I was prime minister, I'd be the first prime minister in living memory who has been an entrepreneur by background.
"Doing deals is my bread and butter as someone who has set up their own business."
Mr Hunt, who is expected for formally launch his campaign on Sunday, added: "The first three businesses I set up failed so I know what it's like to have a business that isn't working out, not to be able to pay your employees their salary at the end of the month, to realise that your products aren't selling.
"I've had all those experiences but what do you learn? You learn to keep going."
"We can never take no-deal off the table but the best way of avoiding it is to make sure you have someone who is capable of negotiating a deal."
Later on Sunday, Michael Gove is expected to enter the race to become Prime Minister on Sunday, where his supporters expect him to declare his candidacy at an event at the Hay Festival.
According to the Telegraph, the Environment Secretary is telling MPs he is the "unity" candidate that can bring the party together on Brexit and stop their decline in the polls.
His candidacy would make him the sixth Cabinet or former Cabinet minister to enter the race, with more expected to announce their entry into the already crowded field.
- War of words between leadership hopefuls turns sour
As the battle heated up, International Development Secretary Mr Stewart said he could not serve in a government led by Boris Johnson because of his stance on a possible no-deal exit from the EU.
He told ITV News: "Boris has many, many skills but one thing I would not call him at the moment is a unifying figure.
"His policies are for a no-deal Brexit, which is going with the (Nigel) Farage wing of our party."
The comments came as Labour insisted it would force a Commons vote of no confidence in the new prime minister as soon as possible.
Mr Stewart had earlier told BBC Radio: "I spoke to Boris, I suppose, about two weeks ago about this and I thought at the time he had assured me that he wouldn't push for a no-deal Brexit.
"So, we had a conversation about 20, 25 minutes and I left the room reassured by him that he wouldn't do this.
"But, it now seems that he is coming out for a no-deal Brexit."
Work and Pensions Secretary Amber Rudd ruled herself out of the contest, but Matt Hancock announced on Saturday that he was in the running.
Mr Hancock said he would take a different approach to try to get Commons support for a Brexit deal rather than the tactics Mrs May used.
He told ITV News: "Bringing the country together is absolutely critical for the next leader, and, of course, the party.
"And to do that, we need to deliver Brexit but not be defined by Brexit."
He said Brexit needed to happen before any general election, which would be a "huge risk" for the Conservative party.
Mr Hancock said he was the man to "unite the country and the party by being completely straightforward" with what needed to be done and the trade-offs.
More than a dozen Tories are understood to be considering a bid.
The new Tory leader looks set to take over as prime minister at the end of July after a tearful Theresa May finally laid out a timetable for her exit from Downing Street on Friday.
Former foreign secretary Mr Johnson, who has emerged as the bookies’ favourite, stressed he would be prepared to back a no-deal departure to ensure the UK leaves the EU on October 31.
The timetable for the contest will see nominations close in the week of June 10, with MPs involved in a series of votes to whittle down what is set to be a crowded field to a final two contenders.
Tory party members will then decide who wins the run-off.