The chief executive of British Airways has criticised what he calls the "perverse logic" of London Mayor Boris Johnson's plan for a new airport in the Thames Estuary.

Writing in The Independent newspaper on Monday, Willy Walsh said the idea had been around since the 1960s and no one had yet produced practical proposals for making it happen.

Mr Johnson's plan, dubbed "Boris Island," would mean a new London airport on an island in the Thames Estuary, two miles off Sheerness and close to the Isle of Grain.

Mr Walsh said:"No new runways have been built at major South-east airports in the past 60 years. In the meantime, air travel has increased exponentially and is now as vital to the success of the UK as the shipping lanes were in the early industrial era.

"Our nearest European neighbours have national hub airports with four or five runways. Not only can they offer direct flights to more destinations, but they have enough spare capacity to prevent minor disruptions causing massive knock-on delays. Is the answer a new national hub in the Thames estuary? 2

Mr Walsh said the current Government had considered and rejected the idea in 2002-03. It was dropped on environmental grounds and costs, which would have to cover new rail and motorway links to London. Estimates have ranged from £40bn to £70bn.

The chief executive added:"Such a sum could never be raised from the private sector alone. And how could the Treasury justify such investment when a large hub airport with good road and rail links already existed at Heathrow? The perverse logic of the Thames estuary case requires that, to ensure airlines actually used the new airport, Heathrow would have to close.

"So as well as pouring astronomical amounts into the Thames, we would lose the value of past investment into motorway, rail and Tube links to Heathrow, and the £4.3bn invested in Terminal 5.

"A third runway at Heathrow would be entirely privately funded. It would meet strict safeguards on noise and local air quality and – because of the EU carbon trading scheme – would not lead to any net increase in overall CO2 emissions. The proposal has massive support from business and unions, and has been subject to public scrutiny for six years. It is time to get on with it."