It may not be quite Homer Simpson in the hot chair but some key US nuclear staff could be less qualified than they seem, a congressional report has found.

Investigators have established that 28 top federal employees including nuclear monitors possess bogus college degrees and the phenomenon may be much bigger.

Staffers have been buying degrees from unaccredited US colleges which are usually based on "life experience".

The report examines how federal funds have been used to purchase them.

The "diploma mills" often use names similar to those of accredited schools and largely award degrees on the basis of a person's existing career, the report by the General Accounting Office (GAO) says.

Such colleges ask for little or no academic work of their "students".

While the federal government does pay for employees to pursue further education, it may by law only do so with regard to schools approved by a recognised accrediting body.

'Joke'

The report to the Senate Committee on Government Affairs, which does not name any "graduates", was compiled between July 2003 and this February and involved an undercover investigator.

It says that three senior employees with emergency security roles and security clearances at the National Nuclear Security Administration possess bogus degrees.

One told the GAO he had obtained a master's degree for $5,000 though he had neither attended classes nor sat tests.

The certificate, drawn up on the basis of his "life experience" and past studies and described by the man himself as a "joke", helped him to advance in his career.

The GAO concludes that federal agencies lack proper systems to verify degrees, or to uncover payments for degrees masked as fees for training courses.