THERESA May needs to “get a grip,” reassert her authority and sack Boris Johnson or stand aside for someone who can, the Liberal Democrats have insisted.

The call from Alistair Carmichael, the Lib Dems' Chief Whip, came after it was claimed that four of the Prime Minister's closest Cabinet colleagues planned to replace her in a swift coup after the Tories’ poor General Election performance in June.

The four alleged conspirators were Boris Johnson, Philip Hammond, David Davis and Amber Rudd.

In a 4am text message the day after the election, the Chancellor is said to have indicated to the Foreign Secretary that he was prepared to back Mr Johnson if he ran for the leadership.

An insider who discussed the matter with Mr Hammond that morning said the Chancellor thought the Foreign Secretary should head a triumvirate in which Mr Davis "could run Brexit, he could run the economy and Boris could run the shop".

The source added: "I know on that first day he thought Boris could be the answer because he'd have this reach and appeal."

However, the plot came to nothing after it became clear Mrs May was not going to stand down and the Brexit Secretary signalled he would not defer to Mr Johnson.

The claims are contained in a new book - Fall Out: A Year of Political Mayhem - which is being serialised in The Sunday Times.

The paper said a source close to Mr Hammond had confirmed his election night backing for the Foreign Secretary, saying: "I'm not going to quibble with that."

But Mr Carmichael, in light of the supposed Tory conspiracy, called on Mrs May to act.

“At a time when we are immersed in the most important negotiation we shall see in our lifetimes we have a Tory government that is in total disarray. This cannot be allowed to go on. Our nation's future is at stake here.

"Theresa May needs to get a grip of her government and make them focus on the job in hand. She should give Boris the boot and reassert her authority. If she cannot do that, then she should stand aside for someone who can.

"Our Cabinet looks more like a bunch of toddlers fighting in a nursery sandpit. Our national interest demands better than this," added the former Scottish Secretary.