LONDON - LONDON'S Lord Mayor Boris Johnson has called for an investigation into the building of a possible sixth London airport to ease congestion.

The Mayor, who was elected in May, said in a newspaper column that the construction of a new airport east of the city should be considered.

'It is ... ever more urgent that we investigate the possibility of a long-term solution, in the form of a new and more eco-friendly international airport,' he wrote in The Daily Telegraph.

He said he doubted that a proposed third runway for Heathrow, the world's busiest airport carrying 68 million passengers a year, would ever be built, while adding that London's second biggest airport, Gatwick, was 'full to bursting'.

He said more detail would be given on the new airport proposal in due course.

A spokesman for the Mayor was not immediately able to comment.

Heathrow, Gatwick and Stansted are all owned by airports authority BAA - the subject of a Competition Commission investigation into whether its monopoly should be broken up.

BAA, owned by Spanish group Ferrovial, is under fire from airlines for its high charges, while many critics feel its efforts to improve infrastructure at its airports would be greater if it was competing for passengers. -- REUTERS