Developer Harry Crosbie has launched a legal action against the National Asset Management Agency.
The move comes just a month after the agency alleged in the Commercial Court that he had failed to disclose assets.
Now Mr Crosbie, through William Fry Solicitors, claims NAMA is in breach of "a solemn agreement" it entered into with him in August 2012.
Mr Crosbie also demands that NAMA cease pursuit of any outstanding debt against him.
If the legal action is successful, the agency will also have to remove its receiver from the Bord Gáis Energy Theatre and compensate Mr Crosbie for alleged leaks made by NAMA of personal information regarding his financial affairs.
Last month, NAMA launched an action in the Commercial Court seeking to recover loans of €77m from the businessman.
The agency claimed that Mr Crosbie had provided it with materially inaccurate sworn statements of his assets, which failed to disclose all the assts held, including property in France.
NAMA was also concerned about alleged payments - amounting to almost €1.4m - from Mr Crosbie to his wife around the time the agency took over his loans. He also did not disclose details of significant cash gifts to his children.
The Commercial Court heard that companies linked to Mr Crosbie owe NAMA about €400m.