Clarke warns May over future if she backs 'hard Brexit'
Former Chancellor Ken Clarke has suggested that Theresa May might not "survive" as prime minister if she sides with "hard Brexit" MPs.
Mr Clarke, a leading supporter of the European Union, told BBC One's Sunday Politics that only a "minority" in the Commons shared such views.
He added it would be "pretty catastrophic" to tell the EU "we're just pulling out".
Mrs May has promised to negotiate the "best possible terms" for Brexit.
The prime minister - who is promising to trigger Article 50 of the Lisbon Treaty, getting formal talks with the EU under way, by the end of March - has also said she is "ambitious" for future relations.
There is much debate over what form Brexit should take, including what access the UK should have to the European single market and the degree of free movement of people that should remain.
Asked whether it was his view that, if Mrs May sided with a "hard Brexit" group, she might not survive, Mr Clarke said: "It is, because I think only a minority of the House of Commons think it's all frightfully simple and that we just leave.
"I mean, the referendum campaign, the only national media reporting on the issues were completely silly and often quite dishonest arguments on both sides."
He added: "She will be in a minority if she started adopting the views of (Eurosceptic Conservative MPs) John Redwood or Iain Duncan Smith.
"It's quite clear that a majority of the present House of Commons does not agree with that, and actually it would be pretty catastrophic if that's all we were going to do - if we turn up and face 27 other nation states in the biggest free market in the world and tell them we're just pulling out."
But Mr Clarke, who backed Mrs May to become prime minister following the win for the Leave campaign in June's Brexit referendum, said: "Theresa's in favour of free trade. She always says that."
He added: "I don't think she will go for a hard Brexit."
Last week, the Commons voted to support the government's timetable for Brexit, with Mr Clarke the only Conservative MP opposing it.
Mr Clarke urged the government to publish a White Paper, "setting out a strategy on which all the cabinet are agreed" before negotiations with the EU begin.
Ministers have said they do not want to give away too much of their position in advance, arguing this could undermine the UK during the process.
Last month, 60 Conservative MPs called for the UK to pull out of both the European single market and the customs union, which allows its members to trade without tariffs but imposes common duties on goods imported from outside the bloc.
One of them, Suella Fernandes, MP for Fareham, said: "As was made clear in the referendum campaign, remaining in the EU's internal market like Norway, or in a customs union like Turkey, is not compatible with either of these commitments and doing so would frustrate the will of the electorate."
In June's referendum, 51.9% of voters chose to leave the EU, with 48.1% opting for the UK to remain a member.