(Bloomberg) -- Boris Johnson has not even entered Number 10 Downing Street as Britain's prime minister and already he is facing a battle to keep the government he hopes to lead alive.If, as expected, Johnson is named Conservative leader on Tuesday and becomes prime minister on Wednesday, he will inherit a country in crisis and a governing party so divided that some members fear it could break apart.The leadership contest, in which Johnson is competing with Foreign Secretary Jeremy Hunt, has deepened the splits within the party over Brexit. Those tensions are likely to increase as the clock ticks down to the Oct. 31 deadline for leaving the European Union.While Johnson's allies prepare for a fight, one minister threatened to try to topple the next administration rather than allow the new premier to take Britain out of the EU without a deal.'I hope we never get there, but I think a lot of people were taught that you must put the interests of the country above yourself,' health minister Stephen Hammond told BBC radio on Friday.Hammond said he would be 'very cautious' about backing a motion of no confidence in his own party's administration -- but did not rule it out. If such a motion were passed, it would put Britain on course for a general election.DivisiveJohnson is a divisive character in the U.K. -- and especially among the Conservative ministers and MPs he works with. He served as foreign secretary for two years, where Theresa May regarded him as a destabilizing influence, and some of his former Cabinet colleagues still treat him with deep suspicion.Their main concern is Johnson's vow to take the U.K. out of the EU by Oct. 31, even if it means leaving without an agreement.Some ministers, including Chancellor of the Exchequer Philip Hammond, are likely to resign or be fired if Johnson takes over as leader. Once they are freed from the requirement to be loyal Cabinet colleagues, they will join a growing army of rebel Tories who are determined to fight to stop a no-deal Brexit.These rebels -- who could include May herself -- will have little to lose from defying Johnson's orders and might feel few reservations about doing so, given how often he has rebelled over Brexit.No-Deal RevoltIn an interview with France's Le Monde and Germany's Suddeutsche Zeitung newspaper published on Friday, Philip Hammond said he would do 'everything in my power' to block a no-deal Brexit. He declined to rule out the possibility of voting to bring down a Johnson government if necessary. 'I do not exclude anything for the moment,' he said.The first clear sign of the likely revolt came on Thursday when more than 30 Tories defied party orders and helped pass a measure intended to stop the next leader forcing through a no-deal Brexit by suspending Parliament -- something Johnson hasn't ruled out.In response to the risk of a mutiny from within, some Johnson allies are trying to change Conservative Party rules to shore up his position as leader.Nigel Evans, a Conservative MP on the committee overseeing party leadership elections, said 'a discussion' is under way about giving the new leader a one-year grace period before he can be challenged. Under current rules, Tory MPs can trigger a vote of no confidence in the leader immediately -- in theory.Evans, a Johnson supporter, told Sky News there would be 'an immense amount of anger' among grassroots party members if MPs tried to overthrow the leader they had just elected.(Updates with Chancellor Hammond's comment in 11th paragraph.)To contact the reporter on this story: Tim Ross in London at firstname.lastname@example.orgTo contact the editors responsible for this story: Flavia Krause-Jackson at email@example.com, Stuart Biggs, Mark WilliamsFor more articles like this, please visit us at bloomberg.com2019 Bloomberg L.P. Click here to read full news..