Theresa May is running a "government with no policies" and no idea how to carry out Britain's exit from the European Union, Tory grandee Ken Clarke has warned.

In a scathing attack on the Conservative administration, the former chancellor also took a sideswipe at the so-called "three Brexiteers" - Foreign Secretary Boris Johnson, Brexit Secretary David Davis and International Trade Secretary Liam Fox.

Mr Clarke said the Prime Minister was saddled with an "appalling problem" in getting the trio to work together and highlighted the difficulties she faced on maintaining party unity given the demands by "ultra-Eurosceptics".

Brexit planning could cost £65m a year

And the pro-EU MP revealed he would vote against Brexit in the House of Commons, branding the referendum an "opinion poll" and David Cameron's decision to hold the vote "catastrophic".

:: Brexit planning may cost £65m a year, study says


His comments come ahead of the Conservative Party conference in Birmingham, amid divisions over whether to pursue a so-called "hard Brexit" outside the European single market or to remain part of it.

In an interview with the New Statesman, Mr Clarke, who is stepping down at the next election, said: "Nobody in the Government has the first idea of what they're going to do next on the Brexit front."

Schulz: 'No negotiation before notification'

He warned the three cabinet ministers charged with delivering Brexit that "serious uncertainty in your trading and political relationships with the rest of the world is dangerous if you allow it to persist".

On party splits over Brexit, Mr Clarke said: "Whatever is negotiated will be denounced by the ultra-Eurosceptics as a betrayal."

He added: "Theresa May has had the misfortune of taking over at the most impossible time.

"She faces an appalling problem of trying to get these 'three Brexiteers' to agree with each other."

He also singled out Mr Johnson and his former Vote Leave ally Michael Gove for giving "respectability" to "(Nigel) Farage's arguments that immigration was somehow a great peril caused by the EU".