A former government minister is suing RTE and the State over a court case in which a jury found he was partly responsible for the defamation of a Sinn Fein political manager.
In proceedings initiated this week, Labour politician Joe Costello claimed he was denied the right to defend himself in the high-profile action taken by one-time Provisional IRA member Nicky Kehoe.
Mr Kehoe sued RTE over an episode of the Saturday With Claire Byrne radio show in October 2015 in which he claimed he was falsely described by Mr Costello as the IRA's former chief of staff in Dublin.
In the ensuing trial in February 2018, Mr Justice Bernard Barton made a significant ruling in which he found the former Labour Party TD could be described as a "concurrent wrongdoer".
A jury later awarded Mr Kehoe €10,000 damages.
This was reduced to €3,500 as the jury also found RTE was only 35pc responsible for the defamation. Mr Costello, a former junior trade minister, was found to be 65pc responsible.
However, he did not have to pay any compensation as he was not a defendant.
The former Dublin Central TD has now issued proceedings against RTE, the State and the Attorney General, claiming he was denied fair procedures and natural and constitutional justice as he had no opportunity to defend himself.
Mr Costello claims his polit- ical credibility and reputation were damaged by the finding, and he had not been invited back on any RTE current affairs programmes.
During the defamation trial, Ms Byrne said she thought Mr Costello had "gone doo-lally" when he claimed a former chief of staff of the IRA in Dublin was directing councillors on how to vote at meetings.
Mr Costello did not identify anyone by name, but Mr Kehoe's name was introduced to the discussion by Sinn Fein TD Eoin O Broin, who gave an impassioned defence of his party colleague.
Within minutes, Mr Costello climbed down on the claim.
Ms Byrne also read a clarification at the end of the show.
However, the jury found Mr Kehoe had been defamed because the contents of the broadcast meant he was not a fit person to be involved in the democratic process.
In proceedings initiated on Thursday by Mr Costello's solicitors, the politician is seeking a declaration that his constitutional rights were breached.