Exclusive: Theresa May allies dismiss Boris Johnson's Brexit red lines as 'political posturing'

Mr Johnson hit back at the criticism, telling The Daily Telegraph that it is "extraordinary that so much of a fuss" is being made about his intervention.

It came as a senior ally of Mrs May insisted that Mr Johnson's Brexit red lines are in fact similar to the Prime Minister's approach to Brexit.

The ally said: "It's all eminently do-able, this is just straw-man posturing from Boris to raise his profile. There's no conflict here, that's why she won't be sacking him."

However other ministers said that Mr Johnson's intervention had directly undermined the Prime Minister's authority.  One said: "His red lines are insubordinate and undeliverable. He is trying to undermine her."

The Prime Minister yesterday sidestepped the question of whether Johnson was “unsackable” in a broadcast interview marking the start of the Conservative Party conference in Manchester.

She told the Andrew Marr Show on BBC One that he was "absolutely behind" her plan for Brexit. She said: “What I have is a cabinet that are united in the mission of this government, and that is what you will see this week.”

In his article the Foreign Secretary has said a transition period after Brexit should last “not a second more” than two years and warned that the UK must not accept European rulings during that time.

However a senior ally of Mrs May claimed that Mr Johnson's Brexit red lines are in fact close to Mrs May's approach. New EU laws and regulations are unlikely to come into force during the transition period because they take five years or longer to enter the UK's statute books, the source said.

The ally said: "It's all eminently do-able, this is just straw-man posturing from Boris to raise his profile. There's no conflict here, that's why she won't be sacking him."

Mr Green, the Prime Minister's right-hand-man, yesterday rebuked Mr Johnson for his intervention.

He said: "I am happy to make a general point that it is understandable that any group of politicians faced with a big issue will have a range of views.

"It is extremely sensible when you are in government to express those views in private rather than public.

"It’s advice for everyone. It’s advice for all my colleagues at all times. That if you feel strongly about something then make your pitch in private. And then, when the government has come to a collective decision, stick to it."

Mr Johnson was also criticised by David Mundell, the Scottish Secretary, who suggested that the Foreign Secretary would be unable to win young voters.

He highlighted the fact that Mr Johnson once stood as a candidate to become rector of Edinburgh University but lost.

The Foreign Secretary, asked about the suggestion that he should have kept his red lines private, told The Telegraph: "I think actually if you studied what I said, it was basically government policy. I think it's extraordinary that so much fuss has been made about repeating government policy, but there you go."

The Prime Minister yesterday insisted that it had not been a mistake to call the snap election that lost the Tories their majority in the Commons, issuing only a qualified apology for the bungled campaign. She said: "I am sorry that some very good members of parliament lost their seats."

But Mrs May denied calling the poll had been a mistake, telling Marr: 'Is it ever a mistake to give people the opportunity to vote? I don't think so. At this stage, of course I wanted to see a different result and I had hoped for a different result in the general election."

Ruth Davidson revealed her mobile phone texts with Boris Johnson in an attempt to quash claims of a rift between the pair and move the focus of the Tory conference away from the leadership “psychodrama”.

Challenged on the BBC’s Sunday Politics Scotland programme that the interview had been interpreted as an attack on Mr Johnson, she insisted that she and Mr Johnson agreed it was "mischief".

Pressed about whether Mr Johnson’s recent interventions on Brexit, in which he has laid down a series of ‘red lines’, were consistent with collective ministerial responsibility, she said he had a right to speak out on issues within his brief.

“The reaction to what I was saying yesterday is a prime example of how the media are wanting to make divisions where there are none,” she said, before claiming the Cabinet was united behind Theresa May’s Brexit blueprint. It came as the British Chambers of Commerce warned that Cabinet splits risked undermining business confidence and Brexit negotiations.