Plans for a new �2bn international airport to serve Wales and the west of England have been formally submitted to the UK Government.

The Severnside airport plan - which could be open by 2012 - would be built near Newport, south Wales, with runways on a man-made island in the Severn Estuary.

It makes sense to locate a major airport at the western end of the M4 corridor Severnside chairman Michael Stephen

It would be sited near to the Corus steelworks plant at Llanwern.

Backers of the scheme say it could handle 30m passengers a year by 2030 and help create 13,000 jobs.

The would-be developers face a tough fight to get the project accepted.

Transport Minister Alistair Darling said last summer that the proposal was unlikely to get the green light - and would only go ahead if airports at Cardiff or Bristol closed down.

Alistair Darling : "unlikely" to go ahead

A final decision on just which airport schemes nationwide get the go-ahead will be made in Westminster in an aviation White Paper expected later this year.

Severnside's chairman Michael Stephen said on Monday that the Government had shown "a fundamental misunderstanding" of the Severnside proposal.

"They are quite right that Cardiff and Bristol airports can handle the local demand, but neither of them are well located and neither can connect directly with a motorway or mainline railway," Mr Stephen said.

"Severnside will not, repeat not, be a regional airport. It will be an intercontinental airport, doing for southern and western England and south Wales what Manchester airport does for northern England and north Wales."

'Makes sense'

"As the area in the UK with the greatest number of people wishing to fly is spreading out westward from London, we believe it makes sense to locate a major airport at the western end of the M4 corridor.

"The roads, rail and airspace in the south east, especially in London and on the M25, are already seriously overcrowded."

The developers argue there would be huge savings on aviation fuel because transatlantic jets will not need to fly the 260-mile round trip to Heathrow.

And, as Severnside would have uncongested airspace, aircraft would not need to stack in the air on arrival or burn fuel on the ground awaiting departure.

Cardiff Airport would have to close for the plan to go ahead

There would also be savings of road fuel, they claim, as 65% of passengers from Wales and the west had to travel to the London airports.

Road access to Severnside would be from the M4, M5 and M48 motorways via short dedicated spurs to the terminal.

Rail access would be via the airport's own mainline station directly alongside the terminal.

Friends of the Earth Cymru have voiced their opposition to the plans.

Campaigners said the project would have a detrimental impact on the local environment, wiping out 780 acres of mudflats vital to numerous wading birds.

They pointed out that the proposed site and surroundings were covered by an Special Protection Area for birds.

Roads giving access to the airport would have to cross a Site of Special Scientific Interest, while the Severn Estuary was also a proposed Special Area of Conservation.

But Severnside chairman Mr Stephen said: "It is not true that access routes would wipe out areas of scientific interest as we would use existing roads from junctions 23A and 24 from the M4."