Six Irish passports may have been compromised by a Russian spy ring uncovered in the US earlier this year, it emerged today.
Three people have been caught up in the diplomatic scandal, including a Donegal firefighter and his wife and a female volunteer with the To Russia With Love charity.
But Garda detectives suspect up to another three passports may have been copied by agents and data stolen for forged documents.
The identities were used by Russian spies living in New York, Boston, New Jersey and Virginia and unearthed after a 10-year "deep-cover" secret service operation in June.
All 10 suspects were later deported in a spy swap deal with Moscow after admitting being foreign agents.
Foreign Affairs Minister Micheál Martin said the use of Irish identities in a spy ring was of grave concern.
"Any story that involves the compromising and undermining of our passports security situation and that, in any shape or form, steals the identification of Irish citizens is a matter of deep concern and is disturbing," he said.
The Department of Foreign Affairs refused to comment on individual cases but said investigations, involving officials at the Passport Office, were ongoing.
The Russian Embassy in Dublin declined to comment on the scandal but praised the work of the To Russia With Love charity and its founder Debbie Deegan.
"We really appreciate what Ms Deegan and her organisation does. We understand that she is, has done, and is going to do a lot of noble work and charitable assistance in our country. We really highly respect her organisation," an Embassy spokesman said.
It is the second forged passport scandal to hit innocent Irish citizens after an alleged Israeli assassination squad from the Mossad intelligence agency killed a Hamas militant Mahmoud al-Mabhouh in Dubai. Some of them travelled on cloned Irish papers.
Justice Minister Dermot Ahern said it was vital the integrity of the Irish passport was upheld.
"The Government is determined that there would be no interference of the Irish Passport, either by Israel or Russia," Mr Ahern said.
"Irish people are entitled to be able to travel abroad with their passport, which is internationally recognised. The importance of the authenticity of our passport isn't to be interfered with."
The compromised passports are believed to be the older style passports - not the biometric documentation introduced by Mr Ahern, then Foreign Minister, in 2005.
Biometrics were introduced in 2006 to safeguard against fraudulent applications. It includes a number of important security features designed to protect identities, including data in a microchip embedded in the photo page and facial recognition.
Mr Ahern said he was aware of the situation and discussed it with Garda Commissioner Fachtna Murphy in Donegal.
Court papers lodged in the US after the spy ring was uncovered claimed one of the 10 arrested, Richard Murphy, was told by handlers to travel from the US to Rome where he would be given forged Irish documents.
It was an old style paper with a laminate over a simple passport photograph and no biometric information.
A passport owned by Donegal fireman Eunan Gerard Doherty, from Carndonagh, was apparently cloned to allow the spy known as Mr Murphy to covertly get into Russia.
Mr Doherty had travelled to the former Soviet state on a family holiday in 2005. Data from his wife Maureen's documents were also copied.