Everybody understands that we have no choice

John Collingwood, FBI spokesman

FBI Director Louis Freeh has also ordered reviews of all sensitive investigations to determine if agents have accessed information outside their normal duties, reported the newspaper.

The new requirement follows last month's arrest of Robert Hanssen, a veteran FBI counter-intelligence agent accused of selling information to Moscow.

Immediately afterwards, the US Attorney General, John Ashcroft, summoned a panel of experts to review internal FBI procedures and recommend changes.

Mr Hanssen is alleged to have spied for Moscow since 1985 - in all that time he was never given a polygraph test.

'Never again'

Some experts believe he might have been caught earlier with the aid of a lie-detector test.

Since 1994, people applying for jobs at the FBI have had to submit to lie detector tests, while other employees are examined on a case-by-case basis.

Alleged spy Robert Hanssen: Never took a test

But observers say that until now the FBI, unlike the CIA, had resisted calls for wider use of this kind of test within the agency.

But FBI spokesman John Collingwood told the Washington Post: "No one wants to do anything that indicates mistrust in employees, but everyone recognises that we have had a serious breach here."

"We have to make sure it doesn't happen again," he said.

The process is expected to be completed within 60 days, and from now on agents are to be submitted to tests every five years.