The race to become the next Conservative Party leader has begun, following Theresa May’s announcement that she will step down next month.
Health Secretary Matt Hancock is fifth Tory to enter the race.
He told the BBC that delivering Brexit was “mission critical” and Mrs May’s successor must be more “brutally honest” about the “trade-offs” required to get a deal through Parliament.
The leadership contest will determine who is the UK’s next prime minister.
Party bosses expect a new leader to be chosen by the end of July.
Mrs May confirmed on Friday that she will resign as party leader on 7 June, but will continue as PM while the leadership contest takes place.
How the new Tory leader will be chosen
She agreed with chairman of the Tory backbench 1922 Committee, Sir Graham Brady, that the process to choose a new leader should begin the week after she stands down.
Five candidates have, so far, confirmed their intention to stand:
Foreign Secretary Jeremy Hunt
International Development Secretary Rory Stewart
Health Secretary Matt Hancock
Former Foreign Secretary Boris Johnson
Former Work and Pensions Secretary Esther McVey
‘Fresh face’ needed
Announcing his candidacy, Mr Hancock ruled out a snap general election in order to resolve the Brexit stalemate, saying this would be “disastrous for the country” and would risk seeing the Labour leader Jeremy Corbyn in power “by Christmas”.
Instead, he said his focus would be on getting a Brexit deal through the current Parliament and “levelling” with MPs about what this would mean for the UK.
He told Radio 4’s Today programme he would push harder on alternative arrangements to the Northern Irish backstop but also be more upfront than Mrs May had been about what compromises the UK would have to make.
Image copyright Reuters
Image caption Amber Rudd is not standing but wants to shape the debate on Brexit
He said there was no point in becoming prime minister unless he was straightforward about the trade offs – “between sovereignty and market access and the trade-offs to get a deal through this Parliament”.
He also said the party needed a “leader for the future not just for now”, capable of appealing to younger voters.
“We need to move on from the horrible politics of the last three years,” he said.
“We need a fresh start and a fresh face to ensure this country wins the battles of the 2020s and remains prosperous for many years to come.”
Mr Stewart warned other candidates to tell the truth about what a no-deal Brexit would mean.
“There are huge tensions in the race,” he told Radio 4’s Today.
“People will be encouraged to promise things they can’t deliver… the most dramatic of which are people who are going to be encouraged to promise a no-deal Brexit.”
What May’s exit means for Brexit
Kuenssberg: May was overwhelmed
He said Parliament would simply not vote for leaving the EU without a deal and, even if the UK did leave that way, it would leave the country in a limbo.
“It is not a destination. It is a failure to reach a destination. What they are probably promising is failure, delay and endless uncertainty.”
Media captionTheresa May: How the PM fought through Brexit battles
More than a dozen more senior Conservatives are believed to be seriously considering running – including Sir Graham, who has resigned as chair of the 1922 Committee.
Most bookmakers have Mr Johnson as favourite, in front of former Brexit Secretary Dominic Raab and Environment Secretary Michael Gove, who has yet to declare his hand.
Work and Pensions Secretary Amber Rudd has ruled herself out, telling the BBC the party and the country wants “someone who is more enthusiastic about Brexit than I am”.
Asked who she would support, she told Radio 4’s Today she would “not malign” any of the candidates but would prefer someone who “wants to find a compromise” on Brexit and be realistic about what can be achieved”.
‘Do things differently’
Tory MPs have until the week commencing 10 June to put their name forward, and any of them can stand – as long as they have the backing of two parliamentary colleagues.
The candidates will be whittled down until two remain, and in July all party members will vote to decide on the winner.
The Conservative Party had 124,000 members, as of March last year. The last leader elected by the membership was David Cameron in 2005, as Theresa May was unopposed in 2016.
It will be the first time Conservative members have directly elected a prime minister, as opposed to a leader of the opposition.
Announcing her departure in Downing Street, Mrs May urged her successor to “seek a way forward that honours the result of the referendum” and seek “consensus” in Parliament.
Contender Mr Johnson told an economic conference in Switzerland on Friday that a new leader would have “the opportunity to do things differently”.
Outlining his Brexit position, he said: “We will leave the EU on 31 October, deal or no deal. The way to get a good deal is to prepare for a no deal.”
Meanwhile, shadow chancellor John McDonnell suggested Labour might need to harden its position on another Brexit referendum if the Tories elected someone willing to pursue a no-deal exit.
Mr McDonnell told Today that “some form of public vote” would definitely be needed in that situation and he would seek to talk to MPs from all parties to potentially try and bring down a government that tried to take the UK out without a deal.