Boris Johnson has accused the government of trying to kick a decision about a new airport into "the long grass" until past the next election.
He told BBC Two's Newsnight this was down to the coalition leadership trying to "appease their ideological environmental wing" of both parties.
The Mayor of London said he believes his colleagues in central government appear to be "tip-toeing back towards the electrified fence of the third runway," and says that if they go ahead they will get "the most powerful shock".
Mr Johnson says he will "die in a ditch" to prevent a third runway and instead urges the government to discard the coalition agreement and consider expanding at Stansted or Gatwick as an interim solution ahead of any new airport built in the South East.
He also dismisses a suggested proposal that RAF Northolt - close to Heathrow - should be brought into use as a third runway for Heathrow.
Some time in the summer the government is due to publish a consultation paper on expanding airport capacity in the South East. It is a fraught issue for the coalition.
Conservative cabinet ministers, including Education Secretary Michael Gove and Northern Ireland Secretary Owen Paterson, have demanded in recent meetings that the government expand airport capacity in the South East as a means to galvanise investment in the UK economy - both through a large infrastructure programme and through the economic activity it might enable. They are said to have persuaded the chancellor of the merits of their case.
The coalition agreement rules out the building of the third runway - something the Conservatives campaigned against at the last election and which the current Transport Secretary, Justine Greening, vociferously fought against. Her Putney constituency would be affected.
The mayor has long championed an idea of a new four-hub airport which, if built, would double the current capacity of Heathrow, something industry insiders have said risks undermining Heathrow.
Now Boris Johnson is renewing his bid for government backing, but says he believes his colleagues may not make a decision. He also voices fears they are looking again at the building of a third runway instead of backing his idea of an airport in the Thames Estuary, so-called "Boris Island".
"Let me explain what is happening", he said. "They are trying to long-grass it. Their whole strategy is that this is simply too difficult.
"It's difficult because they are trying to appease their ideological environmental wing - some of them in the Tory party some of them in the Lib Dem Party. They want to keep every ball in the air until past 2015. That's the strategy as far as I understand it."
On the government taking a second look at the building of a third runway at Heathrow, Mr Johnson said:
"I think it is very difficult for a government to go against the wishes of the population by greatly expanding an airport slap bang in the middle of London suburbs.
"London is unlike any other capital in the world. We ask our planes to fly in over the city and land in the western suburbs. Nobody else does it that way - it is an historical accident.
"We should not aggravate that mistake. I think there is now a risk that the government is going to tip-toe back towards the electrified fence of the third runway - you can hear some of the mutterings from some people in the Treasury and the Department for Transport - they are testing the water, to mix my metaphors.
"But when they get to that electrified fence they will have a most powerful shock. It is not deliverable - now or in the future, the third runway is, as they say in Brussels, Caduck. It is dead, it is over, move on."
Acknowledging it could take 15 to 20 years to build, he accepts there must be some "stop-gap" solution, and says that ideas ruled out by the coalition - such as the building of extra runways at either Stansted or Gatwick - might need to be reconsidered.
"In reality, you're probably looking at 15-20 years. That's with a certain amount of electro-convulsive shock therapy to the whole thing," he said.
"If we had a bit of get up and go we'd do it in six years. That's how quickly we did it in Hong Kong."
Mr Johnson told Newsnight: "You've got an irresistible force in the form of businesses desire to do this, you've heard what [Richard] Branson has to say.
"All my time as mayor I've been lobbied by business - this country's economic drivers, who say, 'We've got to have more airport capacity, particularly in the South East'. And then we've got the immovable object which is public aversion to a third runway at Heathrow.
"Politicians like me who will die in the ditch to prevent that from happening because it really would be a disastrous solution. So that means you've really got to look at alternatives and that's why the government is very sensibly having a review.
"You should not exclude the possibility of a clean, green, eco-friendly 24-hour hub airport. Conveniently located down river. Offering the chance to entrench this city's lead as the greatest economic commercial capital in Europe.
'Quality of life'
"The stopgap has to be some sort of expansion somewhere in the perimeter of London. I've got a very open mind. I understand the arguments from business that you need an interim solution, but what I don't accept that a third runway can't be that interim.
"It will cause huge numbers of extra planes over the City, because everybody knows that once you get an interim solution it will be permanent. Nothing survives like a provisional solution. It will greatly erode the quality of life."
Asked what that stop gap might be, given the expansion of Stansted and Gatwick have been ruled out, the mayor said: "Don't forget the coalition has moved quite some way already in the last few years because it began with a policy of no more runways anywhere ever in the South East. That was patently not economically sustainable.
"I think the coalition has moved quite a long way - not just Lib Dems who have been taking that line but many of my friends in the Conservative Party. I don't think that's economically sustainable."
When asked what would happen to Heathrow if his new four runway airport were built, Mr Johnson said: "You are creating a new hub airport... doesn't mean Heathrow couldn't be a local airport. But in terms of a new hub that would not be at Heathrow."
Watch Allegra Stratton's full interview with Boris Johnson on Newsnight on Monday 28 May at 22:35 BST.