The Moriarty tribunal has accused businessman Denis O'Brien of acting "wrongfully and unlawfully" in the course of interviews he did with four Sunday newspapers two weeks ago. One of the interviews appeared in the Sunday Tribune.

A major row has now erupted between O'Brien and Moriarty with solicitors for the businessman writing to the tribunal on Friday demanding that it retract this allegation.

The day after the interviews appeared, the Moriarty tribunal wrote to O'Brien's legal advisors, Meagher Solicitors, accusing O'Brien of "wrongfully and unlawfully" disclosing information regarding the substance of the tribunal's provisional findings.

O'Brien's solicitors say they are "very perturbed" at the accusation which is "not acceptable" and without legal basis.

"The tribunal is a tribunal of inquiry and as such its findings... represent no more than a reasoned and informed expression of opinion... and are... devoid of legal effect. Put simply, it is not for the tribunal to find that our client has broken the law."

O'Brien's solicitors further argue the tribunal has breached their client's constitutional and natural rights in reaching this finding as O'Brien was not furnished with a copy of the evidence supporting this allegation and was not allowed to make submissions on this issue and that the tribunal effectively "prejudged the matter".

Strongly rejecting that O'Brien "knowingly breached the confidentiality" of the tribunal findings, Meagher solicitors say the tribunal never previously said there was any prohibition on disclosing the "substance of the provisional findings".

Citing 18 different examples, they also argue that a "plethora of articles" in Irish and British newspapers put the substance of the provisional findings in the public domain prior to O'Brien's interviews.

"Yet to our knowledge the tribunal has not taken any action against these newspapers for acting 'wrongfully' or 'unlawfully'."

The letter warns if the tribunal were to refuse to circulate O'Brien with any fresh or amended provisional findings, it would be acting "disproportionately and illegally".