Independent TD Mick Wallace has "no evidence" to support claims of malpractice against Nama staff, the agency said on Friday.
Mr Wallace told the Dáil that he had named up to 20 Nama staff whom he claimed were engaged in "serious malpractice" in a letter to the agency's chairman, Frank Daly, on November 9th.
However, a Nama spokesman described the letter as the latest in a series of attempts by Mr Wallace to discredit the organisation that had no evidence to support them.
“Nama has always treated with the utmost seriousness any claim of wrongdoing supported by evidence,” the spokesman said.
“Nama cannot do so in this case as the deputy has never provided any such evidence, despite our many requests that he do so.”
A letter to Mr Wallace from Nama's head of legal, Aideen O'Reilly, points out that if he has information on any criminal offence, the law obliges him to tell An Garda Síochána.
She adds that if it does not relate to a crime, he should bring it to Nama’s attention so that it can investigate it.
Ms O’Reilly warns that the letter could be construed as defamatory of those he names, which could leave it open to them to take legal action.
Mr Wallace said that his letter to Mr Daly asked if any of the staff that he named had been reported to the Garda.
During Leaders' Questions in the Dáil, Mr Wallace outlined what he said were details of a series of emails between former Nama adviser, Frank Cushnahan and an Asian businessman.
Mr Wallace said that he had travelled to Asia to meet the businessman and collected emails and documents.
Mr Cushnahan was a member of Nama's Northern Ireland Advisory Committee until November 2013 and is a key figure in the controversy over the agency's sale of its Project Eagle loans to Cerberus for €1.6 billion in 2014.
The controversy blew up when Mr Wallace first highlighted claims that business and political figures in Northern Ireland were to benefit from the deal. Project Eagle is the subject of investigations here, the United States and the United Kingdom.