British Prime Minister Theresa May will try to salvage her Brexit strategy on Wednesday when she takes the stage at the Conservative Party conference to fend off rising opposition to her plan and hang on to her shaky leadership.
"It would mean that United Kingdom business and industry, our entire economy, would be exposed perpetually to regulations that might have been expressly designed at the behest of foreign competitors to do them down", Johnson told the Conservative Party conference in the English city of Birmingham.
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.
"I passionately believe that our best days lie ahead of us and that our future is full of promise", she will say.
"If we cheat the electorate, and Chequers is a cheat, we will escalate that sense of mistrust."
"We must show everyone in this country that we are that party", Mrs May will declare.
In response, Mrs May said the ex-foreign secretary could be relied upon to put on a "good show" but parts of his speech - which she says she did not watch - had made her "cross".
Mr Johnson, who became the figurehead for the campaign to leave the European Union, has been one of her loudest critics.
"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".More news: Mourinho insists he does not fear the sack at United
'They want to support a party that is decent, moderate and patriotic.
His fellow Scottish Conservative MP, Ross Thomson, was among those to greet Mr Johnson at the event. This is not what we voted for.
"We can not, must not and will not let this weaselly cabal of superannuated Marxists and Hugo Chavez-admiring, anti-semitism-condoning Kremlin apologists anywhere near the government of this country".
He added: "I don't think this is a time to be talking about leadership challenges, it is a time to be supporting our Prime Minister as she takes forward this incredibly hard task of getting a deal with the European Union".
Naming Margaret Thatcher, the prime minister from 1979 to 1990 who remains a hero to many in the party, he called on Conservatives to build more houses and, while courting business, he struck out at bankers over the 2008 financial crisis. "No, because I think we probably can't have the self-indulgence of a leadership challenge".
Verhofstadt mocked Boris Johnson's latest proposal for a bridge to Ireland saying that he was well-known for proposing plans for bridges, but was "better at burning them".
Michael Edwards from Hastings, a Tory member for 40 years, said Johnson gave an "inspiring speech".
But Mr Mundell said Mr Johnson was "not an asset" to the party in Scotland.
And he contrasted the "real excitement" at Mr Johnson's fringe speech with the "empty" main conference hall.