In an attempt to lay to rest controversy about his military service, it released 30-year-old personnel records which officials claim prove that he did fulfill his duties to his country.

But it appears to have stirred further questions about the claim that he failed to finish his National Guard service.

In a further blow yesterday, Bill O'Reilly, a high-profile anchor on the rightwing Fox News Channel, said he had lost faith in Mr Bush's pre-war claims about Iraq.

The president's predicament has been exacerbated by the expectation of an election contest in November against John Kerry, a Vietnam war hero.

The White House released payroll and retirement records from Mr Bush's Vietnam-era service in the Texas Air National Guard to try to end questions about a "lost year" in his military service nearly 30 years ago.

Doubts have been in circulation for 10 years. National Guard service was a desirable assignment, since its recruits were spared duty in Vietnam.

The present controversy, which concerns Mr Bush's whereabouts for 12 months from May 1972, was given new life on Sunday when the president promised a television interviewer that he would release his military records.

At a raucous press conference yesterday, the White House released the payroll and personnel documents. They are the first evidence that Mr Bush appeared for duty between May 1972 and May 1973.

But they do not directly answer reports from two of Mr Bush's commanding officers that they could not evaluate his performance because they did not observe him on duty.

A story in yesterday's Boston Globe said Mr Bush got credit for attending drills, despite notes from commanders saying he did not appear for duty at Texas and Alabama bases.

The White House claims may not carry much weight with a generation which recalls service in the National Guard as a way to avoid Vietnam.

Richard Cohen, a Washington Post columnist, wrote yesterday that he barely turned up for his stint in the guard after six months' basic training. "For two years or so, I played a perfectly legal form of hooky," he wrote. "To show you what a mess the guard was at the time, I even got paid for all the meetings I missed."

Mr Bush's present travails date from January 20, when he delivered a weak state of the union address. His evasion on the Vietnam war echo his statements on Iraq.