It is understood the businessman and former Libertas leader Declan Ganley is planning to sue RTÉ for defamation.
According to reports in the Sunday Independent, the legal action relates to a 'Prime Time' programme, which aired in November 2008, during the Lisbon Treaty Referendum.
Mr Ganley believes that the programme contained "extremely serious, defamatory allegations" against him.
He also accuses the 'Prime Time' team of attempting to discredit him both personally and professionally and undermine his opposition to the Lisbon Treaty.