A FURTHER round of Tory infighting erupted yesterday after Boris Johnson issued a blistering attack on Theresa May’s Brexit strategy – just days before the Conservative Party conference.

The former foreign secretary, who quit the Cabinet in July, described the Prime Minister’s Chequers plan as “a moral and intellectual humiliation for this country” that will “cheat the electorate” if implemented.

He accused the UK Government and civil service of a “pretty invertebrate performance” in negotiations and said there had been “a collapse of will by the British establishment to deliver on the mandate of the people”.

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In a 4500-word column in the Daily Telegraph, entitled “A better plan for Brexit”, Johnson set out an alternative vision which he said would make Britain “rich, strong and free”.

As a priority, he urged the UK Government to ditch Chequers and negotiate a Canada-style free deal which would “fulfil the instruction of the people”. Johnson wrote: “Overall, the Chequers proposals represent the intellectual error of believing that we can be half in, half out: that it is somehow safer and easier for large parts of our national life to remain governed by the EU even though we are no longer in the EU.

“They are in that sense a democratic disaster. There is nothing safe or ‘pragmatic’ in being bound by rules over which we have no say, interpreted by a federalist court. The Chequers proposals are the worst of both worlds. They are a moral and intellectual humiliation for this country. It is almost incredible that after two years this should be the opening bid of the British Government.”

Johnson also argued for a new withdrawal agreement which states that the Irish border question will be settled as part of the deal on the future economic arrangements – a position already rejected by the EU.

He said the implementation period should be used to negotiate and bring into force a “SuperCanada”-type free trade agreement and that MPs should not vote to hand over £40 billion to the EU without any such agreement.

Former cabinet minister Nicky Morgan mocked the ex-foreign secretary, while arch-Brexiteers such as Jacob Rees-Mogg rallied to his defence. Morgan tweeted: “I said Boris had to decide if he was a politician or a journalist. He’s clearly made his decision but shame he didn’t research the link between agreeing a solution that keeps the Irish border frictionless and the chances of agreeing withdrawal terms. Or does he just not care?”

Rees-Mogg, who chairs the Eurosceptic European Research Group, said negotiations had been “badly con- ducted and likened the Chequers plan to Count Dracula, saying it “doesn’t have much life in the sunlight”.

The new row comes after the current Foreign Secretary, Jeremy Hunt, called for calm over the Brexit impasse, claiming there was always going to come a point in negotiations “where everyone was looking into the abyss”.

May’s plan was publicly rejected by EU leaders in Salzburg last week and both Labour and Tory Eurosceptics said they would vote against any such proposal.

Meanwhile, Scottish Brexit Secretary Mike Russell said staying in Europe’s single market and the customs union is the only “credible plan” to avoid the “twin disasters” of a no-deal Brexit or a so-called blind Brexit.

With six months to go until the UK formally leaves the EU, Russell criticised Tory leaders at Westminster over their “chaotic, disastrous” departure plans. Russell said the majority of Scots were still opposed to Brexit, and that Scottish ministers had “offered compromise after compromise” to the UK Government during its Brexit preparations, but that this had “so far, all been refused”.

Russell said: “It beggars belief that, six months out from Brexit, the UK Government still has no workable plan and no clear way to achieve any sort of agreement with the EU.”

Russell added that even a trade deal similar to that between Canada and the EU “would leave every single person in Scotland £1600 a year worse off compared to staying in the EU”.