The interminable examination of airport capacity in the south-east of the United Kingdom reached a new stage earlier, with both London Heathrow Airport and Gatwick Airport claiming momentum.

As the Airports Commission opened a three week public consultation on its latest research, Heathrow claimed expansion there would deliver more “economic benefits” and jobs to the UK, while Gatwick claimed Londoners would rather see a second runway built there.

However, the latest report from the commission warned both proposals could be significantly more expensive than planned.

The Airports Commission argued a second runway at Gatwick would cost £2 billion more than the bid suggests, while two separate plans to expand Heathrow are predicted to cost £3-4 billion more.

Alternative proposals, including building new airports near Oxford or in Thames Estuary, have already been ruled out.

Three options remain - a second runway at Gatwick, a third runway at Heathrow, or an extension to one of the existing Heathrow runways.

No decision has yet been reached on which to recommend, with a final report due after the 2015 general election.

The head of the commission, Sir Howard Davies, explained: “We have not yet taken a view on which proposal strikes the most effective balance between the assessment criteria.

“It is important first that we provide an opportunity for this evidence to be examined, challenged and improved.

“This consultation gives everyone with an interest in the issue of airport expansion that opportunity.”

Claiming success for its proposals, Heathrow chief executive John Holland-Kaye said: “The Commission has confirmed that only Heathrow can connect all of Britain to global growth, delivering over £200 billion to the British economy and 180,000 jobs while reducing noise for local residents compared to today.

“This shows that Heathrow’s proposal is deliverable and is the only way to keep Britain at the heart of the global economy.

“Now it’s time for all those who want a better future for Britain to make their voice heard and back Heathrow.”

The Commission puts the economic benefit of a new runway at Heathrow at £112-£211 billion.

This is a significantly higher figure than previously estimated.

Most economic benefits would accrue outside London and the South East.

PWC analysis for the Commission says Heathrow expansion could deliver up to £114 billion of economic benefits to Scotland, Wales, Northern Ireland and the English regions.

Drawing Gatwick’s conclusions from the same report, chief executive Stewart Wingate said: “The Airport Commission’s consultation published today underlines why momentum is gathering behind Gatwick’s case for airport expansion in the south-east.

“The UK gets the economic benefit it needs at a fraction of the environmental impact of Heathrow today.

“It would mean competition and lower fares for passengers.

“We have a financing plan and a construction project that can be delivered without huge risk to the public purse.

“After decades of indecision, the UK needs something to happen.

“As the Commission underlines Gatwick can actually be delivered by 2025.”

The report notes that Gatwick’s scheme has the flexibility to accommodate a range of business models and airline types, and would result in “roughly a doubling of existing capacity at Gatwick and is sufficient to meet the Commission’s assessment of need for new capacity by 2030”.

The Commission also estimates there could be wider benefits within the economy up to £127 billion.