London mayor Boris Johnson says Gatwick and Stansted should be expanded as stop-gaps ahead of any new airport built in the south east of England.

But he accused the government of trying to kick a decision about a new airport into “the long grass” until past the next election.

Johnson told BBC Two’s Newsnight this was down to the coalition leadership trying to “appease their ideological environmental wing” of both parties.

He said he believes his colleagues in central government appear to be “tip-toeing back towards the electrified fence of the third runway” at Heathrow and says that if they go ahead they will get “the most powerful shock”.

Johnson said he will “die in a ditch” to prevent a third runway at Heathrow and instead urged Whitehall to discard the coalition agreement and consider expanding at Stansted or Gatwick as an interim solution ahead of any new airport built in the region.

He also dismissed a suggested proposal that RAF Northolt – close to Heathrow – should be brought into use as an akternative third runway.

The mayor has long championed an idea of a new ‘Boris island’ hub airport in the Thames estuary which would double the current capacity of Heathrow.

But he accepted that 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.

Johnson, speaking out head of the government’s plans to publish a consultation paper on expanding airport capacity in the south east tis summer, told the BBC: “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.”

Asked what would happen to Heathrow should a new four runway airport be built, 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.”