Taoiseach Enda Kenny has described allegations of bags of cash being paid to a former adviser to Nama as incredible and extraordinary.
Mr Kenny said he was not opposed to an inquiry into the handling of Project Eagle, the biggest property deal in Northern Ireland when US investment giant Cerberus paid Nama £1.2bn (€1.4bn) for a loan portfolio in 2014.
The sale was first dogged by controversy after £7m (€8.2m) linked to it was found in an Isle of Man bank account.
Subsequently BBC Spotlight reported a series of taped conversations between developer John Miskelly and Frank Cushnahan, the former member of Nama's Northern Ireland advisory committee, including one about a handover of £40,000 (€47,200) cash in a hospital car park.
Mr Kenny said he had watched the programme.
"I found it quite incredible," he said.
"Nothing surprises me at the kind of activities that take place in politics, in that sense I find it extraordinary to hear the audio reports of engagements and meetings between certain personnel."
Project Eagle has been examined on several occasions at the Public Accounts Committee in Dublin.
The Comptroller and Auditor General (C&AG) ran its own audit of the same. Its report, which is due to be examined by cabinet ministers this week, is expected to find that taxpayers lost out on hundreds of millions of euro.
Fianna Fáil leader Micheál Martin has joined calls from opposition politicians for an inquiry.
Mr Kenny told Kfm: "If I find or our colleagues in Government find that this is a case that has to be examined then I won't be opposed to that.
"If there are questions arising from the Public Accounts Committee engagement with Nama, and they are due before them shortly, I'm not averse to taking action, but I need to know what it is I'm taking action on."
Mr Cushnahan has denied any wrongdoing.
Nama is due to appear before the Public Accounts Committee (PAC) on September 22 and its executives are also to be questioned at the Oireachtas Finance Committee, chaired by John McGuinness, a former PAC chairman.
Investigations have been launched into Project Eagle by the UK's National Crime Agency, the US Department of Justice's Securities and Exchange Commission as well as a parliamentary inquiry in Stormont.