First Minister Rhodri Morgan has rejected criticisms of the decision to locate a £16bn armed forces training academy in the Vale of Glamorgan.
The academy in St Athan will provide a central training base for the RAF, Army and Navy and is the biggest investment made in Wales, creating 5,000 jobs.
But some English MPs have criticised the process which saw St Athan triumph over rival bids.
They attack government part-ownership of the consortium behind St Athan bid.
Mr Morgan said there were "no foul means" involved in the bid, which was backed by politicians from all parties.
Defence Secretary Des Browne's announcement in the Commons on Wednesday that St Athan had won contracts to train thousands of military personnel was hailed by politicians in Wales who said it would benefit the Welsh economy as a whole.
Welsh Secretary Peter Hain said it was a "tremendous" opportunity adding that the range of jobs created as a result of the military academy would be huge.
He said: "I can't think of anything that offers everything to everybody except this one and for St Athan to have won it fair and square is terrific news, the best news we've had in a very long time."
But some English MPs have questioned the process which saw St Athan triumph over RAF Cosford in Shropshire and Blandford in Dorset.
Technology company QinetiQ, in which the UK Government has a 19% holding, is part of the consortium behind the St Athan bid.
The academy is predicted to provide an economic boost to the area
Bob Walter, Conservative MP for North Dorset, has said the decision is "fundamentally wrong" while Conservative MP Mark Pritchard, whose Wrekin constituency contains the Cosford air force base, has called for the auditor general to investigate.
He said: "Much of the process by which this decision has been undertaken has been very questionable in some areas.
"That's why I have asked the auditor general to investigate, especially in relation to the government having a conflict of interest."
First Minister Rhodri Morgan rushed aside such claims.
He said: "This is an extremely obscure point, it has been examined by government lawyers and found to be worthless.
"This is not a contract that has been subsidised by us [assembly government].
"It's strongly supported by us because we're the landowners and because it helps us develop a civilian aerospace park next door on the rest of the site.
"But there are absolutely no foul means involved in this and the motivation for doing it is entirely because successful consortium Metrix was the only one of the bidders who had the imagination to accept our vision of putting both training packages on the one site."
Mr Morgan added that the Vale of Glamorgan area was fully prepared for the influx of thousands of extra civilian and military personnel who would move to the area in the ahead of its 2012 opening.
He added: "I understand there were 10,000 RAF servicemen and women at St Athan 30 years ago and at peak there will be 10,000 people at this new university campus.
"I don't think it's going to much different from what St Athan was a generation ago."
A union has also claimed that military training instructors could take industrial action over the decision to site the new academy at St Athan
Paul Bemrose from the PCS union said industrial action could take place because staff are angered over redundancies at bases elsewhere in the UK.
"We are probably looking at 19 sites to close around the country, 2,000 potential compulsory redundancies among the existing staff," he said.