The CBI has given its backing to plans for massive expansion of London's Heathrow and Stansted airports.

The business group said on Monday that the plans being considered by the government are the best way to meet the predicted increase in demand for air travel during the next 30 years.

It again warned that the UK's competitiveness is under threat because of the failure in recent years to provide additional airport capacity.

Heathrow must remain a global hub airport with capacity to offer the number of flights crucial to businesses, the CBI argued.

The group said three new runways are now needed in the south east - the first by 2015 - and called on ministers to encourage greater use of regional airports to meet local demand.A new airport at Cliffe in Kent, one of the options being considered by Alistair Darling, was rejected as a potential "white elephant" which would not be cost-effective.

Its report warned the airline industry that it would have to meet environmental commitments as part of any expansion programme.

Digby Jones, the CBI's director general, said expanding capacity was crucial.

"We either respond to growing demand or face being left behind. In addition, Britain's position as a world leader in aviation is under threat unless we act. Foreign competitors would welcome our dissatisfied customers with open arms," he said.

"The south east has the strongest market for UK aviation and the greatest concentration of airlines. It must be maintained as a globally competitive hub to provide vital access to international markets, encourage inward investment and support tourism."The Independent also reported on Monday that one of the options also being considered was a new £800 million airport at Redhill, near Gatwick, to complement any expansion at Heathrow or Stansted.

The private aerodrome, which currently handles helicopter and small aircraft, could be upgraded to a full-scale airport for domestic and European flights.

The plan could circumvent a ban on expansion at Gatwick which landed the government in the High Court last month. Ministers had their decision to exclude Gatwick from its options which forced them to rethink options.

Backers of the plan say fewer houses would have to be demolished and operations could be running within four years of planning permission being given.