SEVENTY local authorities have come out in favour of the Cliffe airport option to solve Britain's airport needs.

Their decisions has caused a major row with Medway and Kent councils who are against the plan. SASIG - the Strategic Aviation Special Interest Group - says Cliffe is a once-in-a-lifetime opportunity and a bold approach to solving the problems of airport expansion. Both Medway and Kent councils have resigned from it.

Rodney Chambers, leader of Medway, said: "We have withdrawn from SASIG because the view being expressed was not in the best interests of the community we represent."

Mott MacDonald, which built Hong Kong's new airport, examined the Cliffe plans for Kent. They found that the proposed airport would cost £16 billion to build, £3 billion more than the Government estimate, and would involve raising marshland by 45ft - a massive undertaking which would not be ready until 2018.

Kent County Council leader Sandy Bruce-Lockhart said: "SASIG was set up to defend Heathrow against expansion."

Meanwhile, a High Court judge has reserved judgement on whether or not Gatwick should be among the Transport Secretary's proposals. Firm decisions on UK airport expansion will be made next year by Transport Secretary Alistair Darling in a White Paper expected in the summer.

SASIG's report says that local opposition should not be a reason for the Government to avoid taking "difficult decisions".

The group claims mitigation measures for bird life - by flooding the Wantsum channel - would be less than a quarter of the cost of compulsorily buying 15,000 homes for a new Heathrow runway.

It said Cliffe was an opportunity to build an airport on a site that has adequate land, but which would impact on a much smaller number of people than developing existing airports.