The proposal for an airport on the Isle of Grain received a major setback today after experts predicted it could cost up to £2bn to provide alternative habitats for wildlife.

The airport issue is in a crucial phase with the Davies Commission set to rule on London Mayor Boris Johnson’s now-favoured Foster airport blueprint on Grain in the autumn.

But a report published by the government's Airports Commission said it would “radically and irreversibly” change the landscape, which is “noted for its remoteness”.

The environmental impacts study said an airport development was likely to result in adverse effects on international nature conservation sites.

It said setting up compensation areas for the displaced wildlife would be “on a scale unprecedented for any single development in Europe.”

The estimated cost, based on other projects, would be between £70,000 and £100,000 per hectare which would result in a cost of between £149m and £2bn, if the airport was to be built.

The airport proposal has faced strong opposition in Medway where the council has doubled its “war chest” to fight the plan to £100,000.

But the Demand Regeneration in North Kent (DRINK) campaign is supporting the airport plan.

Businessman Clive Lawrence said: “ This is the greatest thing that could happen to Medway.

“If it happens it will take a long time and it will last a long time.

The report is the first of four due to be published this week, looking into different aspects of the feasibility of a Thames Estuary airport.

The Airports Commission examines the need for additional UK airport capacity and recommends to government how this can be met.

It comes just weeks after architects Foster and Partners announced the cost to relocate the wildlife would be just £500m.

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