by political editor Paul Francis

Boris Johnson has rejected renewed calls for a third runway at Heathrow, but insists he is not "wedded" to the idea of a Thames Estuary airport at any price.

The London mayor's latest comments come amid suggestions the government may look again at expanding Heathrow as part of efforts to deal with the demand for extra capacity in the south east.

The reports said the Conservatives were preparing to re-examine their policy in response to business concerns the UK was losing ground to other countries as companies moved elsewhere because of better airport connections.

But Mr Johnson was quick to dismiss the idea in comments that will disappoint those who oppose his idea for a floating island airport off the north Kent coast.

He said: "Heathrow has a great future as a key UK airport. But we cannot endlessly expand it, and cram a quart into a pint pot. A third runway would be an environmental disaster.

"It would mean a huge increase in plans over London, and intolerable traffic and fumes in the west of the city – and it will not be built as long as I am Mayor of London."

Mr Johnson added: "That is why the Government is right to look at all new solutions for extra aviation capacity except the third runway at Heathrow. I look forward to engaging with Justine Greening’s consultation this summer."

But there was confusion over the mayor’s thinking when only a day before the reports about Heathrow, he claimed: "Contrary to popular belief I am not the slightest bit wedded to some remote archipelago in the Thames estuary."

Tim Yeo, the Tory chairman of the energy and climate change select committee, said he had "completely changed" his mind on Heathrow expansion and now believed there was no option but to build a third runway.

He said: "We cannot wait around any longer. We have to get on with this. If we don’t, the Chinese and others will take their business elsewhere. There is no time to delay."