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 United Kingdom out of the customs union, single market and jurisdiction of the European Court of Justice.
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.
But he warned: 'If we cheat the electorate - and Chequers is a cheat - we will escalate the sense of mistrust.
Johnson also set out a way to fight the Labour leader, who solidified the socialist takeover of the Labour party at the opposition's conference in Liverpool last week, pledging lower taxes and a free-market economy that gives people a stake in the country's future and control over their day-to-day life.
Rochford and Southend East MP James Duddridge submitted a letter of no confidence in the Prime Minister, saying that she was "incapable" of providing the strong leadership the party needs.
Mr Johnson said the PM's Brexit blueprint - which ties Britain to a common rulebook with the European Union for trade in goods - would be "politically humiliating for a £2 trillion economy", would lock Britain in the "tractor beam of Brussels" on regulation and would prevent it from making its own laws.
"Unfortunately, Mr Johnson seems to behave in a way that suggests he is only focused on his own self-interest and not on the interests of our country and I find that very disappointing".
In her crucial conference speech, the PM will make a direct appeal to mainstream Labour voters disillusioned by Jeremy Corbyn's left-wing agenda to switch to the "decent, moderate, patriotic" Tories.
But May, who did not watch her former minister, again showed little sign of shifting away from her so-called Chequers plan to keep close ties with the European Union after Brexit, the biggest shift in British foreign and trade policy for more than 40 years.
'I Know You're Not Thinking, You Never Do'
During today's press conference, after his tense exchanges with the two female reporters, Mr Trump finally addressed the issue.
He added: "My fellow Conservatives, this is not democracy".
Mr Johnson renewed his attack on Theresa May's Brexit plan, describing it as a "cheat" that could lead to a boost for the far-right.
He said: "I write this with heavy heart, however we now need a proper leadership election and to move on".
Ms. May has held back on criticizing Mr. Johnson, but on Tuesday, she said his speech had made her "cross". "No, because I think we probably can't have the self-indulgence of a leadership challenge".
"I think he really set the right tone, I was anxious he would be divisive and speak against the Prime Minister".
But Mr Mundell said Mr Johnson was "not an asset" to the party in Scotland.
The wide-ranging speech was widely seen as Johnson's audition for May's job before the party faithful at their annual gathering.
Mrs May is set to make a bid to rally the party behind her in what is seen as possibly the most important speech of her political career, in which she will say that Britain's post-Brexit future is "full of promise".