An airport in the Thames Estuary will be one of the options considered in the government's aviation strategy, Prime Minister David Cameron has confirmed.

Campaigners will be readying themselves for a prolonged battle against the proposal after the announcement which brings to an end years of speculation about whether or not it was on the table.

It also marks a u-turn from Mr Cameron, who ruled out an airport in 2010.

In a speech in London today (Monday), he said he was "not blind to the need to increase airport capacity, particularly in the south east".

Mr Cameron said the UK needed to retain its status as a global hub for air travel, and admitted the course of action would be controversial.

He said: "We will need to take decisions for the long-term and we will be bringing forward options in our aviation strategy which will include an examination of the pros and cons of a new airport in the Thames estuary."

The strategy is expected to be announced sometime after the Budget on Wednesday (March 21).

The idea of an airport off the north Kent coast has been dubbed 'Boris Island', after the Mayor of London Boris Johnson's idea for an airport on floating islands.

Architect Lord Foster, who designed Wembley stadium, wants to construct the world's biggest airport on the Isle of Grain.

In an exclusive interview with the KM Group last year Lord Foster said the airport, which would have four runways and handle 150 million passengers a year, was a realistic ambition, and not "pie in the sky" as it has been dubbed by detractors.

The last time an airport in Medway was looked at was in 2003, when the then Labour government examined an airport at Cliffe. In the end this was ruled out in favour of expansion at existing airports.