Speculation surrounding an airport in the Thames Esutary has increased, after the aviation regulator warned new runways need to be built in the South East to increase capacity.

The Civil Aviation Authority (CAA) said improving facilities at existing airports such as Manston would be a short-term solution.

Additional capacity would offer “significant benefits” for consumers and the economy, it added.

This would include ensuring the UK continued to be able to access global markets.

The CAA did not explicitly mention or back the building of an airport in north Kent, but the comments will increase the speculation surrounding it.

In November Chancellor George Osborne said all options would be considered in an attempt to maintain the UK’s aviation hub status – except for a third runway at Heathrow.

The government’s intentions will become clearer when it publishes its aviation strategy in the spring. The CAA response is part of the government’s pre-publication consultation.

Two plans for an airport in the Thames Estuary have been put forward so far.

The Mayor of London Boris Johnson wants to build a floating airport in the Estuary – dubbed Boris Island.

The world’s biggest airport, which would have four runways and handle 150 million passengers a year, would be built on the Isle of Grain if the architect Lord Foster gets his way (a cross-section image of his proposal is shown above).