Calling on his rival to be more "ambitious" on the economy, the Mayor said in an interview with the London Evening Standard: “The Government needs to stop pussyfooting around.
"The way to get business really motoring in the UK is to cut taxes, cut regulation, create the infrastructure and get behind it. That’s what you should do.
"There’s a real opportunity to capitalise on the Olympics. [To] look at London as the motor that can drive growth.
“This is the time to be ambitious about London and what it can do for Britain. One of the ways of doing that would be to commit to further infrastructure — Crossrail 2, more river crossings, a massive house building programme for the city.”
Last month, the Government delayed the publication of a consultation into the future of Britain's airports, amid reports that Justine Greening, the Transport Secretary, was opposed to the building of a third runway at Heathrow, the option thought to be favoured by Mr Cameron and George Osborne, the Chancellor.
Mr Johnson, who wants to see a new airport built in the Thames to help relieve London's overstretched terminals, described the delay as "totally mad".
Claiming that Mr Osborne is "actually very much up for big ideas like this," and that Miss Greening "gets" the idea for a new four-runway airport, dubbed "Boris Island,", he said the Prime Minister had yet to be convinced, blaming the "institutional inertia of the Government."
"Heathrow is fundamentally not the place" for further expansion," Mr Johnson added. “I think there’s a bit of institutional capture. But it’s a totally blind alley.
“The attempt to try and long-grass it for three years into the other side of the election is just not realistic. Totally mad and it won’t work.”
The Mayor disclosed that Mr Cameron had grabbed him in a bear hug while they posed for photographs during the Games – leading Mr Johnson to grasp the opportunity to hiss in the Prime Minister's ear: "airport."
And he called on the Government to take advantage of the Olympics to cement London's place in the world.
He said: “I think that what the Olympics has done is to confirm in a lot of people’s minds around the world that London is the capital of the planet. What I think the Government should do is make a very powerful statement of ambition for London.”
The poll of 547 Labour supporters by the website LabourList found that 51 per cent agreed with the statement that "Boris would be harder to beat than Cameron," with 22 per cent disagreeing and a further 22 per cent saying it would make no difference.