Stansted Airport is lobbying for a new runway

They claim that airports and airlines will pass on the cost of building new runways to the customer - which could total �4bn.

This week Stansted Airport told the BBC its current airport charge to airlines - at present �2.89 per passenger - will go up by nearly 70% to �4.89 over the next five years to cover added security and shop costs.

Multi-billion pound plans for the airports at Stansted, Heathrow, Luton and Gatwick have been put forward to the government.

A White Paper on the proposals is due to be published in two weeks.

John Williams, a spokesman for Stansted Airport, said: "London airports have some of the lowest landing charges in the world because they are regulated.

Stansted Airport's John Williams believes airlines get a good deal

"So we don't believe that an increase to cover the cost of a second runway would be beyond our airlines."

Campaigners against a second runway at Stansted believe the airport may have to charge as much as �10 per passenger to pay for the new runway.

Brian Ross, of Stop Stansted Expansion, asked: "Is it realistic that they could pay such a price?

"Heathrow is the most expensive of the BAA airports just now. It achieves �6 per passenger.

"The average fare at Heathrow is �400 every trip, at Stansted the average is �40.

"The two airports are totally incomparable and the economics are totally incomparable."

Luton Airport could also be given approval to expand

Peter Mackenzie-Williams, head of aviation at the Transport Research Laboratory, said the cost of airport expansion will be passed on to passengers, but it will be over a long period of time.

He told BBC News Online that it is possible the cost of a new runway at Stansted or Luton could be paid through increased fees in advance of work on the runway starting.

"We are already starting to see increases at Heathrow over the next five to 10 years and it would be reasonable to assume if another runway at Stansted is approved something similar would happen," he said.

Ryanair and EasyJet, the dominant carriers at Stansted, are concerned they will be presented with steep increases to help fund the runway.

A spokesman for EasyJet told the BBC that it will not pay for a runway it does not use.

A Ryanair spokesman said it is fundamentally against passing on any tax rise to passengers.