A senior Irish government official has been working as a British military intelligence spy for the past three decades, according to a former British agent.
The agent, known by the pseudonym Sam Rosenfeld, told the Irish News that a senior government official is a current asset for British military intelligence.
Rosenfeld, who worked for the Force Research Unit (FRU) on both sides of the Irish border, said he visited the Dáil as a guest of the senior official in the past.
He refused to name the official but said British military intelligence is "super sensitive" about the issue.
"I am assuming there's many (spies) still working in the Irish Republic, but one of them holds a very senior position in the Irish government," Rosenfeld told the Irish News.
Rosenfeld added that he recently discovered that the official now holds an even more senior role in the Irish Government than when he was serving with the FRU.
He said he was aware of other spies working on both sides of the border but added that they have "moved on" or "given up".
However, Rosenfeld said the Irish Government official was "still at it".
He told the Irish News that he was not sure how the official was recruited but said he believed the British Embassy in Dublin was involved.
"I have a suspicion, obviously a suspicion is never proof, I have a suspicion of how it came about and that relates to somebody who used to work at the British Embassy in Dublin."
Rosenfeld described the relationship between the Irish official and British military intelligence as a "long-term engagement".
"There are times when you have people and you leave people and you don't bother people and they stay in place and you only have contact every now and again."
Rosenfeld also told the Irish News that he often spied on Irish military bases in the Republic of Ireland while working as an FRU agent. He believes there is little that British military intelligence does not know about Irish affairs.
"I don't think there's anything that the Irish government would have secrets from the British government anyway," he added.