NAMA has accused bust developer Sean Dunne and his wife Gayle Killilea of obstructing inquiries into their financial affairs.
Lawyers for the so-called bad bank claim the couple have attempted to "frustrate, thwart and obstruct" investigations into their finances by a NAMA subsidiary and a court appointed bankruptcy trustee.
The hard-hitting remarks were made in legal filings as the agency formally opposed efforts by Mr Dunne to withdraw from his bankruptcy case in the US.
Although the Carlow-born businessman filed for bankruptcy himself with debts of €695m in March last year, he is now seeking to have the case withdrawn.
Mr Dunne is in the middle of parallel proceedings in Ireland where Ulster Bank had him adjudicated a bankrupt. He claims there is no point fighting the case in the US when his creditors could seek to undermine any American ruling in the Irish courts.
In an affidavit submitted to the US bankruptcy court in Connecticut yesterday, NAMA claimed Mr Dunne's application to withdraw from the bankruptcy process in the US "was filed in bad faith and that a dismissal of the case would prejudice creditors".
The document went on to accuse Mr Dunne of making "false oaths" and of the "transfer, removal and/or concealment of assets".
National Asset Loan Management Ltd (NALM), a subsidiary of NAMA which has been pursuing Mr Dunne for loans of €185m, initiating a court case against him a year and a half ago.
It has gone to great lengths, hiring international corporate investigations firm Kroll to probe the finances of both Mr Dunne and his wife.
The agency has also issued 15 subpoenas or notices of deposition to banks, law firms and business associates of Mr Dunne and Ms Killilea.
It is challenging Mr Dunne's discharge as it believes Ms Killilea is developing property with money fraudulently transferred from her husband. The couple have denied the claim.
In the affidavit, NALM's lawyer Daniel Elliott said debtors did not have the discretion to withdraw from their bankruptcy case once it had commenced.
"Throughout this case and the state court action, the debtor and his wife have attempted to frustrate, thwart, and obstruct inquiry into their financial and business affairs by NALM and the trustee," Mr Elliott said.
He said the trustee, Richard Coan, had gone to court three times to compel Mr Dunne to hand over information, on one occasion requesting that the businessman be held in contempt.
Mr Elliott accused Mr Dunne of "repeated intransigence in discovery".
He added: "Furthermore, the debtor's wife had obstructed all efforts to obtain discovery from third parties."
Meanwhile, at a hearing yesterday, bankruptcy judge Alan Shiff agreed that rulings in Irish family law cases involving Mr Dunne could be submitted to the court "under seal".
The decision means the rulings can be considered by the court, but their contents cannot be publicly divulged. Judge Shiff was told Mr Dunne had no objection.
The rulings are understood to relate to Mr Dunne's divorce from his first wife, Jennifer Coyle. Mr Dunne has confirmed she is a creditor listed as being owed €2.3m by him.