Louis Freeh told the Wall Street Journal that the spying agency's operations in the province had been characterised by decades of "secrecy and non-transparency" and argued against a similar agency being established in the US.

This year MI5 - officially known as the Security Service and to be locally based in Holywood - will take over the lead role in intelligence gathering about national security from the PSNI, including international terrorist threats and terrorist activities within Northern Ireland.

This is the first time that Freeh has so openly criticised MI5, which worked closely with the FBI in operations against the IRA while Freeh was FBI director.

The FBI made the unusual step of releasing Freeh's comments as a Press release on its website.

In an angrily-worded editorial in the Wall Street Journal, Freeh strongly rejected an argument by conservative federal circuit court judge Richard Posner that the US needs its own version of MI5 to fight terrorism.

Describing Judge Posner's idea as "dangerous and dumb", Freeh accused him of having an overly romantic concept of MI5.

"Judge Posner's citation to England's MI5 is romantic enough but needs to be qualified by the long and painful history of its operations in Northern Ireland, which are still unfolding after decades of secrecy and non-transparency," he wrote.

Freeh warned that such an organisation could not be adequately trusted or monitored by the US public, and accused Judge Posner of offering a " long winded thesis" that could not work.

"I suppose that this secret-police agency would appear before Congress in closed sessions and operate with a black budget," Freeh wrote, adding that the American public would never tolerate a CIA-type police organisation operating against US citizens and non-citizens "who live and work under our flag".

He was responding to an editorial by Judge Posner, also in the Wall Street Journal, in which he said that Freeh had tried and failed to get the FBI to take terrorism seriously and that it was now time for a US version of MI5.

Freeh, who resigned in 2001 after nearly ten years as FBI director, has previously worked very closely with British spying agencies and police.

He ran into serious confrontation with President Bill Clinton because of his insistence in prosecuting US-based IRA members during sensitive moments in the Irish peace process.

Both President Clinton and a former Miami FBI chief have publicly acknowledged that Clinton and Freeh had shouting matches over Clinton's opposition to prosecuting four Miami-based IRA gun-runners in the early 1990s.