Boris Johnson has denounced Theresa May’s Chequers plan for EU withdrawal as an “outrage” that would leave the UK “locked in the tractor beam of Brussels”.

In an explosive intervention at the Conservative conference in Birmingham, the former foreign secretary warned that the only winners from a Chequers-style Brexit would be the far-right and far-left in British politics.

And he urged Tory delegates to persuade the Prime Minister to “chuck Chequers” and return to the hard Brexit blueprint she first set out in her Lancaster House speech, when she said she would take the UK out of the customs union, single market and jurisdiction of the European Court of Justice.

Speaking on the fringe of the conference, the former foreign secretary – who quit Mrs May’s Cabinet in July in protest at the Chequers plan – won an enthusiastic reaction on a scale not seen so far inside the main hall.Mr Johnson even won loud applause when he suggested that the PM risked being prosecuted under a 14th century law saying that “no foreign court or government shall have jurisdiction in this country”.

Conservative Party annual conference 2018
Stanley Johnson and Rachel Johnson prepare to watch Boris speak (Stefan Rousseau/PA)

He rejected as “total fantasy” the idea that it would be possible to “bodge” Brexit now and then negotiate a better deal after leaving in March 2019.

And he warned that if a deal based on Chequers was agreed with the EU, it would “embolden” those calling for a second referendum – something he said would be “disastrous for trust in politics”.

Mr Johnson said that Mrs May’s blueprint – which ties Britain to a common rulebook with the EU for trade in goods – would be “politically humiliating for a £2 trillion economy” and would prevent the UK from making its own laws and subject it to the directives of Brussels.

“This is not pragmatic, it is not a compromise. It is dangerous and unstable – politically and economically,” he said.

Boris Johnson
Mr Johnson urged Mrs May to go ahead with her original plan (Victoria Jones/PA)

“My fellow Conservatives, this is not democracy. This is not what we voted for. This is an outrage.

“This is not taking back control: this is forfeiting control.”

And he warned: “If we get it wrong – if we bottle Brexit now – believe me, the people of this country will find it hard to forgive.

He was loudly clapped and cheered as he said: “For one last time, I urge our friends in Government to deliver what the people voted for, to back Theresa May in the best way possible –  by softly, quietly, and sensibly backing her original plan.

“And in so doing to believe in conservatism and to believe in Britain.

“Because if we get it wrong we will be punished. And if we get it right we can have a glorious future.

Conservative Party annual conference 2018
Mr Johnson was mobbed by reporters as he arrived for his speech (Victoria Jones/PA)

“This Government will then be remembered for having done something brave and right and remarkable and in accordance with the wishes of the people.”

A Lancaster House-style Brexit would be a “win-win” for both Britain and the EU, Mr Johnson said.

But he warned: “If we cheat the electorate – and Chequers is a cheat – we will escalate the sense of mistrust.

“We will give credence to those who cry betrayal, and I am afraid we will make it more likely that the ultimate beneficiary of the Chequers deal will be the far-right in the form of Ukip, and therefore the far-left in the form of Jeremy Corbyn.”