BORIS Johnson must stop "exploiting" Theresa May's weakened position, a former cabinet minister has said, as he criticised the Foreign Secretary for "sounding off" over Brexit.

Ken Clarke said that in any normal circumstances the Prime Minister would have sacked Mr Johnson hours after publishing his 4,000-word personal vision for Brexit.

But the Conservative former chancellor added that Mrs May's lack of a parliamentary majority meant she could not easily dispose of Mr Johnson, who was advised to express his Brexit views in private.

Speaking on BBC Radio 4's Today programme, pro-EU MP Mr Clarke said: "Personal publicity and campaigning by the Foreign Secretary is actually just an irrelevant nuisance."

He added enough has been said about Mr Johnson's contribution, which he regarded as a repeat of "one of the more simplistic and dishonest arguments of the hardline Leavers" from the referendum campaign by referring to financial contributions to the EU.

Asked what the PM should do about Mr Johnson, Mr Clarke replied: "They should tell him, if he wants to be Foreign Secretary he should actually make some more serious contributions on wider foreign policy, give his views on the Brexit deal privately - as ministers have always been supposed to do - remember there are rules called collective responsibility.

"Sounding off personally in this way is totally unhelpful and he shouldn't exploit the fact she hasn't got a majority in Parliament, and he knows perfectly well that normally the Foreign Secretary would be sacked for doing that - and she, unfortunately, after the general election, is not in the position easily to sack him - which he should stop exploiting."

Mr Clarke added: "In any normal circumstances he'd have been sacked the day after."