Video report by ITV News Political Correspondent Paul Brand
Theresa May's plans for exiting the EU deliver Brexit "in name only", Boris Johnson has claimed in an explosive resignation speech.
The former foreign secretary lambasted Mrs May's Chequers plan as being a "miserable, permanent limbo" which left Britain an "economic vassal" to Europe.
Speaking in the House of Commons on Wednesday, he said the Chequers plan was a far cry from the vision set out in Mrs May's Lancaster House speech at the end of last year.
And the ex-minister urged the Prime Minister to change tack on negotiations, saying it was "not too late to save Brexit".
Mr Johnson said: "It is absolute nonsense to imagine that we can somehow afford to make a botched treaty now and break and reset the bone later on."
He continued: "We will not be stampeded by anyone. Let us again aim explicitly for that glorious vision of Lancaster House - a strong, independent, self-governing Britain that is genuinely open to the world.
"Not that miserable, permanent limbo of Chequers."
His comments come as Mrs May faces a grilling by MPs in the Commons about her plans for leaving the EU.
Mr Johnson made his speech nine days after his resignation from Cabinet over the Chequers Brexit plan.
His statement had been billed as echoing Geoffrey Howe’s devastating resignation speech after quitting Margaret Thatcher’s Cabinet in a row over Europe – an intervention which contributed to her being toppled within weeks.
ITV News Political Correspondent Paul Brand said the speech was "not a brutal blow", but a "threat to strike later".
Mr Johnson said the Chequers plan would ensure Britain remained "rule takers", and that in many areas "ministers will have no powers to initiate, innovate or even deviate".
He argued that the scope for striking free trade deals was restricted by the Chequers plan, and urge a complete re-orientation of negotiations.
"It is not too late to save Brexit - we have time in these negotiations. We have changed tack once and we can change again," he said.
"The problem is not that we've failed to make the case for a free trade agreement of the kind spelt out at Lancaster House. We haven't even tried.
"We must try now, because we will not get another chance to get it right."
Among the criticisms of the Government's Brexit plan and negotiations thus far, Mr Johnson listed:
Failed to turn the Lancaster House vision into a firm offer;
Agreed to hand over £40 billion with no promise of a future trade deal;
Accepted European Court of Justice jurisdiction over parts of the withdrawal agreement; and
Allowed the issue of the Northern Irish border to dominate the debate.
Earlier, in a heated Prime Minister's Questions, Mrs May faced the wrath of angry backbenchers who accused her of deciding "Brexit means Remain," as Boris Johnson watched on in his return to the Commons.
Labour Party leader Jeremy Corbyn furthered the blow by delivering a scathing retort to Mrs May after she accused him of not listening to anything she said.
“With only three months to go until the final withdrawal agreement is due to be signed the Brexit Secretary (David Davis) has resigned, the White Paper is in tatters, the new Brexit Secretary (Dominic Raab) is skipping negotiations, two years of negotiations with themselves and they wanted to shut down Parliament for five days.
“They’ve even given up negotiating with each other,” he said.
Speaker John Bercow intervened as Tory MPs tried to shout down the Labour leader.
Mr Corbyn went on: “Isn’t it the case that the Government is failing to negotiate Brexit, failing to meet the needs of the country because they are far too busy fighting each other?”
Mrs May replied: “Let me tell you what I’ve been doing over the last week.”
Laughter erupted as Labour MP Emma Hardy was heard to shout: “Panicking.”
Mrs May added to the opposition leader: “While I was agreeing the future of Nato with President Trump, he was joining a protest march against him.
“While I was delivering a plan for our future trade with the EU, he was delivering a plan to teach children how to go on strike.
“And while I was negotiating our future security relationship with Europe, he was renegotiating the definition of anti-Semitism.
“He protests, I deliver.”
The prime minister avoided a damaging defeat on Monday – which could have had major implications for her leadership – by just six votes in the Commons on Tuesday night.
The prime minister now faces an appearance in front of the Liaison Committee of senior MPs on Wednesday.
As Mrs May faces the group, which is made up of senior MPs who chair Commons select committees, a debate will take place in the main chamber on the future relationship between the UK and EU.
Pressure on the PM continued to mount as a poll gave Labour a five-point lead over the Conservatives.
The YouGov poll of 1,657 British adults for The Times, conducted on July 16 and 17, showed how precarious Mrs May's position is:
On a night of high drama in Westminster on Tuesday, the Prime Minister thwarted a rebel Tory move which could have forced her to try to keep Britain in a customs union with the EU by 307 votes to 301, helped by Labour Brexiteers.
But 12 Conservatives broke ranks to back the customs union measure, even though Tory whips told would-be rebels that there would be a confidence vote if it passed – potentially resulting in the collapse of Mrs May’s administration.
Mrs May was defeated on a separate amendment to her flagship Trade Bill, which will require her to seek continued UK participation in the EU’s system for regulation of medicines after Brexit.
Tory chairman Brandon Lewis also came under fire for taking part in the two crunch votes despite being “paired” with Liberal Democrat deputy leader Jo Swinson, who is on maternity leave – an agreement meaning he should have sat out the divisions.
He apologised, claiming it was an “honest mistake” made by the Tory whips in “fast-moving circumstances”, but Ms Swinson said it was deliberate “cheating”.
Theresa May addressed the rule breaking, saying it was "done in error" and not "good enough".