The frontrunner would also skewer Nigel Farage’s hopes of securing any Brexit Party MPs. Rival Jeremy Hunt tonight promised a £27 billion boost for the economy if he wins the Tory leadership race. But the party would lose a general election if he was at the helm even though voters believe he would be a better Prime Minister, according to the ComRes poll. It put the Conservatives on 345 MPs, Labour 207 and the Brexit party at none if Mr Johnson replaced Theresa May.
Under Mr Hunt, the Brexit Party would win 23 MPs while Labour would be 63 MPs short of a majority but would be the largest party.
Some 58 percent believe Mr Hunt would be the best Prime Minister and 63 percent said he was “best manage the economy”.
But Mr Johnson is more trusted to deliver Brexit by October 31 and reduce taxes as well as defeat Jeremy Corbyn.
The poll findings will strengthen Mr Johnson’s hand further as party members wrestle with how to fend off the growing electoral threat they face from the Brexit Party.
Mr Farage led the fledgling group to a victory in the European elections and left the Conservatives humiliated.
The ComRes poll found a third of those planning to vote for the Brexit Party would switch to the Conservative if Mr Johnson becomes leader.
Just six per cent would do the same if Mr Hunt becomes Prime Minister.
Mr Johnson has also now been given the backing of 1,500 Conservative Party councillors and the overwhelming support of Tory MPs.
The leadership rivals will go head-to-head against each other on Tuesday for the first time since the number of hopefuls vying for the top job was whittled down to the final two.
They will be quizzed in a live debate on ITV in front of an audience at 8pm.
Viewers have sent in questions and those chosen will be in the studio to ask them directly.
Around 160,000 Tory party members are eligible to vote in the leadership contest and many are already believed to have filled out their ballot papers but the victor will not be announced until July 23.
Mr Hunt repeatedly challenged the favourite to take part in one to one television clashes earlier in the contest to allow Tory members to see them debating crucial issues before they voted in the contest.
The Foreign Secretary has called on the Conservative Party to remember its role as the party of wealth creators and set out a five point plan to back business.
He pledged reforms that will increase Britain’s productivity that analysis by the Centre for Economics and Business Research consultancy show would deliver a £27 billion boost to the economy.
The Confederation of British Industry has been pushing for investment in “workers, equipment and new technologies” to ensure Britain can thrive after Brexit.
Mr Hunt said: “I’m the man with the plan to turbocharge our economy.
“We can only afford to fund our vital public services if we grow the size of the pot and my plan will do exactly that.
“We have to remember that the Conservative Party should back the wealth creators and entrepreneurs who take risks to create jobs.”
Under the plans taxes on business will be cut to to drive a radical increase in investment, including reducing Corporation Tax to 12.5 percent.
Investment will be ploughed into infrastructure, including completing the High Speed rail link between London and the north and and expanding Heathrow.
Mr Hunt also wants to improve education by reversing the funding cuts of recent years.
And he will encourage entrepreneurialism by encouraging a “risk-taking” culture similar to that of the United States.
As well as reducing red tape he has promised to waive the tuition fees of any graduate that starts a successful business from scratch.
And he plans to instill an “unapologetically and ambitiously pro-growth drive” in Whitehall.
Mr Hunt also pledged to appoint a fishing minister to fight for the industry throughout the Brexit process if he becomes Prime Minister.
The post would be in place at least until the end of the EU withdrawal process, he said.
He said: “If we get this Brexit deal right, there is a sea of opportunity waiting on the other side for our fishermen.
“Until Brexit is fully delivered, I will appoint a fisheries minister with the sole responsibility of fighting for what is best for fishing communities.”
Speaking at a leadership hustings on Monday night, Mr Johnson said he is confident of getting a Brexit deal through parliament.
“I have to keep blowing my own trumpet, there’s no other way of doing this,” he said.
“We already have more than half of the parliamentary party behind us. It’s kept growing. I’m delighted to say it’s both Remainers and leavers who are coming to our side.
“You can already see the makings of a giant coalition and an inclusive one of all the Tories in parliament plus many supporters on other benches.”
Mr Johnson said he’s prepared to be “hated” as Prime Minister.
“It’s not just prepared. I’m already well accustomed to it. Believe me, I’m thick-skinned,” he said.