A senior Irish government official acting as a spy for the British army would have reached the desks of those at the highest level of the London government, a Belfast-based activist said last night.
The Irish government was also urged by one Dublin politician to "seriously investigate" the claims made to the Irish News by a former British Army agent. But all the major political parties in Dublin failed to immediately respond to requests for comment yesterday.
An ex-Force Research Unit (FRU) agent known by the pseudonym Sam Rosenfeld also says he worked for British military intelligence on both sides of the border
The former agent, involved in a long running legal wrangles with various arms of the British government, revealed the senior Irish government figure is a current British military intelligence asset.
He also says he visited the Dail in Dublin as a guest of the man, whom he refused to name.
"I will tell you what they (British military intelligence) are super, super, super, sensitive about, they have somebody still working, and I am assuming there's many still working in the Irish Republic, but one of them holds a very senior position in the Irish government," he said.
Mr Rosenfeld added that he recently "looked and and they are now even in a (more) senior position than they were previously and they still work for the British government, ie, the army.
"The revelation in today’s edition of the Irish News that the British government recruited a senior Irish government official as an agent of the British Army’s intelligence and agent running unit, the Force Research Unit (FRU), would have been sanctioned by British government ministers at the time," said Mark Thompson, head of Relatives for Justice, the campaign group.
"Additionally, the powerful Whitehall based Joint Intelligence Committee (JIC) regularly briefed senior members of successive Downing Street administrations, including cabinet ministers and even prime ministers.
Under international law this constitutes a "very serious diplomatic incident" in that the UK have been, and presumably are still, engaged in international espionage in what they term a foreign country on our island, Mr Thompson said, adding the Irish government can put in place a process to encourage anyone with its civil service to come forward.
"Crucially, now at a time of significant political change, with Sinn Féin on the cusp of becoming the largest political party on the island, it would be naive to think that the hand and influence of the British state was somehow dormant," he added.
Aontú leader Peadar Tóibín TD has called on the new Taoiseach to expel British spies from Irish government buildings.
Deputy Tóibín said: "Revelations that British agents are operating in our government buildings in Dublin are extremely concerning and could seriously damage British-Irish relations.
"The new Taoiseach Leo Varadkar, together with the new Minister for Defence, Micheál Martin, need to seriously investigate this matter"