BORIS Johnson has savaged Theresa May’s blueprint for leaving the European Union, branding it "fantastical" and insisting: “It is not too late to save Brexit.”

The former foreign secretary said the Prime Minister’s plan for close relations with the EU would lead to a “miserable permanent limbo” and urged her to tear it up and focus instead on taking back control.

But Mr Johnson’s comments – made during his resignation statement in Westminster after he quit the cabinet last week – received a mixed reaction from within his own party, as well as scathing criticism from opponents.

Scottish Tory deputy leader Jackson Carlaw branded him a "busted flush".

Addressing MPs, Mr Johnson hailed Mrs May’s “courage and resilience” – before attacking her proposals for a softer Brexit, which he had previously agreed to during talks at her Chequers country house earlier this month.

He did not make a direct challenge to Mrs May's position, but said her plans amounted to a "Brexit in name only" which would leave the UK in a state of "vassalage".

Accusing the Government of "dithering" over the negotiations, he said a "fog of self-doubt" had descended on Mrs May's stance on EU withdrawal since she first set it out in a speech at Lancaster House last year.

He said: “Indeed, the result of accepting the EU’s rule books, and of our proposal of a fantastical Heath Robinson customs arrangement, is that we have much less scope to do free trade deals – as the Chequers paper actually acknowledges, and which we should all acknowledge.

“Otherwise we continue to make the fatal mistake of underestimating the intelligence of the public, saying one thing to the EU about what we are really doing, and pretending another to the electorate.”

He added: "It is not too late to save Brexit. We have time in these negotiations. We have changed tack once and we can change again."

Mr Johnson was sitting close to the spot where former Chancellor Geoffrey Howe delivered his devastating 1990 resignation speech, credited with helping to bring down Margaret Thatcher.

But Mrs May was not present in the chamber to hear his statement, as she was answering questions on Brexit from senior MPs at a long-planned hearing of the House of Commons Liaison Committee.

During his 12-minute speech, Mr Johnson set out a scathing attack on the negotiations so far, insisting the Government had agreed to hand over £40 billion with no promise of a future trade deal and had allowed the issue of the Northern Irish border to dominate the debate.

He called on MPs to “explicitly aim once again for the glorious vision of Lancaster House, a strong independent self-governing Britain that is genuinely open to the world, not the miserable permanent limbo of Chequers, the democratic disaster of ‘ongoing harmonisation’ with no way out and no say for the UK.”

He added: “That was the vision of Brexit we fought for; that was the vision the Prime Minister rightly described last year. That is the prize.

“And if the Prime Minister can fix that vision once again before us then I believe she can deliver a great Brexit for Britain, with a positive and self-confident approach that will unite this party, unite this House, and unite the country as well.”

He said Mrs May's plans would restrict ministers' powers to initiate, innovate or deviate from the Brussels rule book to the extent that they would never again be able to institute a reform programme of the type introduced by Margaret Thatcher in the 1980s.

The statement will be seen as announcing Mr Johnson’s intention to put himself at the head of Tory backbench forces.

He was congratulated afterwards by Scottish Tory MP Ross Thomson, who called it a “historic and excellent personal statement”.

Jacob Rees-Mogg, leader of the influential European Research Group of Tories, also hailed it as "the speech of a statesman".

But Scottish Tory deputy leader Jackson Carlaw branded the former foreign secretary a “busted flush” and insisted it was time to deliver Theresa May’s Brexit blueprint.

He said: “The enthusiasm drained visibly from the surrounding faces as [Mr Johnson’s speech] rambled on.”

Labour's David Lammy said: "Boris Johnson's after-dinner speaking fee must have plummeted faster than the pound after that dreary, self-important resignation speech."