INTERNATIONAL aviation consultants, who worked on the successful development of Hong Kong's new airport, have advised that Cliffe is a completely unsuitable and unsustainable option in the search for increased air transport capacity in the South East. Mott MacDonald has completed a 150-page study of the implications of siting a new London airport at Cliffe on the North Kent marshes. They conclude that the Government's consultants have under-estimated the cost of developing an airport at the site by at least £3 billion bringing the total involved to more than £16 billion. Even using the original figures, development at Cliffe represents by far the worst value for money of all the major options being considered. Financing of the project is probably not achievable without a substantial public sector subsidy. The proposed programme of opening in 2011 is unrealistic as it suggests Cliffe would be quicker to build than the new airport in Hong Kong and that is before allowing for the UK's protracted planning process. A further 80,000 to 110,000 new homes would be needed in Kent, Essex and Medway over and above those already planned. The massive earthworks across the marshland required for the airport could have serious implications for the flood protection of the Thames Estuary including London. The impact on the internationally-acclaimed ecological habitat of the Hoo Peninsular would be quite unacceptable. Sandy Bruce-Lockhart, Kent County Council leader, said: "Cliffe was always blue skies thinking and Mott MacDonald's report now blows this away as a serious option. Unlike other options, which could be developed stage by stage, Cliffe would have to be created in a big bang style. That is because of the incredible cost implications and the need to have an airport with four or five runways right from the opening day to start getting the returns on the investment. "Now, Mott MacDonald are saying that even if the go-ahead was given today the airport would not be operational until 2018. So Cliffe provides no solution to the immediate problem of finding increased runway capacity in the medium term." Chris Chalk, Mott MacDonald's head of aviation services who led the team investigating Cliffe, said KCC had been extremely specific in wanting to ensure the report was a fair and accurate assessment.