Tánaiste and Minister for Defence Micheál Martin has said he has never received a security briefing "saying there's a spy in the Oireachtas".
A report in The Sunday Times alleging that a member of the Oireachtas was recruited as a Russian agent has prompted speculation about their identity.
Mr Martin told the Dáil that "there may be - there may not be" a spy, adding: "I don't know who the individual is."
He also expressed concerns about how the information came to light, saying he had "concerns about how all of this has emerged in the public arena."
Mr Martin was speaking after saying that he wanted to make an important point and statement on the matter.
He said that he was taoiseach during the period in question and received security briefings, "but I was never told and never briefed that there was a spy in the Oireachtas".
Read more: 'There may be a spy in our midst' - Senators declare they are not Russian agents
Responding to Aontú leader Peadar Tóibín, Mr Martin said: "I'm actually very surprised at the degree to which everybody - herd-like - just grabbed on the story and said, 'This is it. Who is the person?'
"I'm absolutely amazed. There's a more fundamental question to be asked, which I'm going to ask as Minister of Defence.
"Because as Minister of Defence, I've never received a security briefing saying there's a spy in the Oireachtas. There may be - there may not be.
"There's an issue of accountability in terms of our intelligence services.
"If this is true, then someone gave that information. And I don't think that's acceptable actually. I don't."
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Future governments "need to be very clear-eyed about the need in a democracy that intelligence services have an accountability chain, and are accountable", he said.
He added: "I would argue, and there is a national security strategy being developed, I would argue that we lack that at the moment.
"I'm not comfortable with the situation pertaining to intelligence. I have concerns about how all of this has emerged in the public arena."
Taoiseach Simon Harris said earlier this week that Russian activity in Ireland should come as no surprise to anyone.
The Sunday Times reported that Russian intelligence allegedly used a "honeytrap" to recruit an Irish politician as an agent during Brexit negotiations, with the aim of undermining relations between Britain, Ireland and the EU.
The paper also reported that while the Irish military and security services identified the potential agent, code-named Cobalt, they remain in the Oireachtas.
Call for training for TDs and Senators
The Ceann Comhairle has been asked to provide training for politicians to better inform them about the methods and risks posed by foreign intelligence actors.
Alan Farrell, who is chairperson of the Fine Gael parliamentary party, wrote to Seán Ó Feargháil on the matter.
The Fine Gael chairman believes that TDs and Senators need to be equipped with the necessary tools to carry out their work in light of the Cobalt controversy.
He said this is necessary to "protect our precious democracy."
