A crucial announcement on the future of UK air travel is set to be made within days, according to David Cameron.

The Prime Minister was addressing an issue raised during today's Prime Minister's Questions in the House of Commons on airport capacity.

It came months after Lord Foster announced a multi-billion pounds scheme to build a huge hub airport in the Thames Estuary.

London Mayor Boris Johnson is also in favour of creating a huge hub in the estuary, to ease pressure on Heathrow and to safeguard the UK's reputation at the forefront of international travel and industry.

But the row has exploded in recent weeks, with talk of building a third runway at Heathrow potentially back on the agenda.

Speaking earlier, Mr Cameron said: "I think what we need to do is build a process that hopefully has cross-party support so we can look carefully at this issue and deliver changes that will address the problems of over-capacitythat we will have in future years, and that address the issue of the hub status of the UK."

He said he was hoping to make an announcement on the issue "over the coming days".

But he stressed it was important that decision makers worked across party lines "because this won't happen unless parties actually sign up to a process that can deliver."

An aerial image of the Thames Hub airport, designed by Lord Foster

If built, Lord Foster's scheme would be built on the Hoo Peninsula and would more than double the capacity of Heathrow, handling up to 150 million passengers each year, 24 hours every day.

It would have four runways, each 4km long, and would have an integrated rail station beneath the passenger terminal.

The UK's busiest airport, it would handle 300,000 arrivals and departures every day.

Boris Johnson's plans are for a hub airport in the middle of the Thames Estuary, off Sheppey.