An Irish police officer has been accused for passing on key intelligence to senior dissident Republicans – thanks to a tip-off from MI5.

The officer was forced to resign from the force after MI5 uncovered his close links to a senior IRA leader in the North.

Ireland’s new Justice Minister Frances Fitzgerald has described the investigation as ‘disturbing’ after the leaked information led to a major security alert.

The Irish Independent reports that the rogue officer passed on information about two dissident Republican suspects as they were being questioned in the Leinster station where he worked.

Minister Fitzgerald has said she is establishing the facts of the situation as a matter of urgency.

She has asked the Interim Garda (police) Commissioner for a full report into the incident.

A statement from her department said: “It would be completely unacceptable if information of any kind were to be passed by a member of An Garda Siochana (police) to members of unlawful organizations.

“It is understood that An Garda Siochana is aware from its own intelligence and enquiries of suggestions that a member of the force passed on the names of persons who had been arrested on a particular occasion.

“The member in question has since resigned and is currently under criminal investigation in relation to this and an unrelated matter.”

The report, first carried in the Herald newspaper, claims the information involved the names of the detained suspects and how long they were being questioned for by detectives.

The officer is reported to have sent a text message to a senior IRA figure based in the North of Ireland.

The text message was picked up by intelligence agencies monitoring phone traffic.

Senior Irish police were made aware of the situation after their Northern Ireland colleagues in the PSNI were tipped off by MI5.

The British state intelligence agency had monitored all calls and text messages to and from the IRA man’s phone.

The PSNI then established that the person who gave the information to the IRA figure was in fact an Irish police officer.

The officer, who has since resigned, is now the subject of investigations into separate serious offenses.

The report says the officer has very close links to a man that was arrested in relation to the 1998 Omagh bombing.

He has also been spotted in the company of a middle-aged Continuity IRA member who previously served a lengthy jail sentence for bomb making.

A source told the Herald: “This garda’s behaviour has caused a huge amount of shock to their colleagues.

“What was happening is highly unusual and is in no way any reflection on the people who were stationed with the garda.”