LONDON: The owners of London's Gatwick airport have challenged Heathrow's investors to explain who will pay £6 billion for the associated road and rail improvements as result of a third runway.

Gatwick says it will meet any additional surface access costs and will be "road and rail ready" for a second runway by 2021. The operator claims Heathrow has already ruled out paying £6 billion for road and rail work required to access the expanded airport, including tunneling the M25 highway.

Now UK transport minister Robert Goodwill has confirmed it won't be the British taxpayer either: "In terms of surface access proposals, the government has been clear that it expects the scheme promoter to meet the costs of any surface access proposals that are required as a direct result of airport expansion and from which they will directly benefit."

Gatwick CEO Stewart Wingate declared: "There is now a £6 billion black hole at the heart of Heathrow's plan. Heathrow has said it won't meet the bill and the now the government has done the same.

"As we approach a decision on expansion, Heathrow owes taxpayers, passengers, airlines and government an explanation of how they plan to meet it as this cost increase alone is almost the entire cost of the Gatwick scheme."

Last year Gatwick published its planned rail and road improvements that it claims will be at no cost to the taxpayer. They include a train to central London every 150 seconds by 2019; rail capacity doubled by 2020, and nearly trebled by 2035; quicker journey times to the West End and City, than from Heathrow; 1000 rail stations within one change, including links to all UK main rail lines, Crossrail and HS2; and planned upgrades to the M25 and M23 highways, including a smart motorway system.

"It is becoming clearer by the day that if we actually want something to be built, and Britain to get the benefits, then Gatwick is the only credible option," added Wingate.