Denis O’Brien claims death threats were made against him and his family after details of his banking affairs with the IBRC were revealed in the Dáil.

The businessman was giving evidence during the third day of his legal action against the State, the clerk of the Dáil and the Dáil’s Committee on Procedure and Privileges (CPP).

During various Dáil debates on dates in May and June last year, Social Democrat TD Catherine Murphy and Sinn Féin TD Pearse Doherty revealed details about his dealings with the IBRC in relation to the sale of Siteserv in 2012.

The revelations were made while a court order preventing RTÉ from reporting those details was in place.

By releasing the information under privilege, Mr O’Brien contends they effectively determined the outcome of his case against RTÉ and he is seeking a number of declarations from the High Court, including one to say that they were guilty of an "unwarranted interference with the operation of the courts in a purely judicial domain".

Mr O’Brien was called to give evidence just after 11.00am today and began by saying he believed this case was "important for the country as a whole".

He compared a person’s banking details to their medical records and said they should be kept confidential.

He described the release of his banking affairs as "upsetting" for both him and his family and said he received death threats after the comments were made in the Dáil.

Under cross-examination by Michael Collins, SC for the clerk of the Dáil and the CPP, Mr O’Brien said he wanted to make sure this never happens again and stressed that he meant that for every Irish citizen.

He said he thought that if you got a High Court order, it wouldn’t be "unravelled by another arm of the State".

He went on to say: "As a citizen, all I want the court to do is to determine whether one can rely on a court order or whether someone can get up in the Dáil and deliberately unravel that".

He said he would like the court to determine whether members of the Oireachtas can breach court orders and denied he wanted to teach TDs a lesson by saying it is about "respecting the High Court".

He finished by accusing Deputies Murphy and Doherty of doing the opposite.

Under cross-examination by Maurice Collins, SC for the Attorney General and the State, Mr O’Brien said the TDs had acted "maliciously and deliberately".

He stepped down from the witness box in front of a packed courtroom at 12.23pm, having spent just under an hour and twenty minutes giving evidence.

The hearing is expected to take at least another four days.