The claims against Mr Callinan come as the Disclosures Tribunal continues to investigate whether there was a Garda campaign to discredit whistleblower Sergeant Maurice McCabe.
Mr McGuinness, former chairman of the Public Accounts Committee (PAC), outlined how he met Mr Callinan in a car park of a hotel the day after his appearance at the committee in January 2014.
The request to meet was made by Mr Callinan but the PAC chairman decided not to tell any of the committee members about it and thought nothing wrong in meeting him.
“When you get a call from the Garda Commissioner, you are inclined not to say no,” said Mr McGuinness.
Sitting in his car, the two discussed PAC, the penalty points scandal, and Sgt McCabe. Mr McGuinness described how Mr Callinan claimed Sgt McCabe had sexually abused his family, could not be trusted, and that he had made a “great error” in getting the PAC involved.
Mr Callinan also gave the impression that there was a file on Sgt McCabe and that action would be taken against him, the tribunal heard.
Mr McGuinness said he was “troubled” by the claims and worried that the PAC might be brought into disrepute over it. He agreed the claims had been “entirely inappropriate”.
“For any individual to accuse someone of the type of abuse Sgt McCabe was supposed to have undertaken and included members of his family — I don’t think anyone could walk away feeling this was OK. I certainly didn’t,” he told Judge Peter Charleton.
Mr Callinan maintains it was Mr McGuinness who first questioned whether Sgt McCabe had a motive about the penalty points system as a file on him had been sent by gardaí to the DPP. The TD denied this.
“How would I know if a file was being sent? I was not a member of the Garda Síochána,” he said.
Mr Callinan also claims it was Mr McGuinness who raised the matter of sexual assault, not him.
Mr McGuinness said that, while driving home after the meeting, he stopped to make notes about the conversation, “out of fear” he would forget it.
The notes record that he wrote several words and phrases, including “sexual abuse”, “individual family”, “don’t trust him’, “investigations ongoing”, and “trouble for PAC and me”.
After thinking over the weekend, Mr McGuinness decided he had a job to do with PAC and Mc Callinan’s claims would have “nothing to do with it”. He decided he believed Sgt McCabe, who had denied the rumours when they met previously.
Mr McGuinness decided not to tell PAC members about the meeting in a bid to prevent rumours spreading. He later informed Fianna Fáil leader Micheál Martin of the meeting.
Meanwhile, Mr McGuinness was quizzed about meeting Superintendent Dave Taylor, former head of the Garda Press Office, who claims he was “used” by Mr Callinan to spread rumours about Sgt McCabe.
Supt Taylor claims he was instructed to draw media attention to a sexual assault allegation against Sgt McCabe to say that this was his revenge “agenda” against the gardaí.
Supt Taylor said instructions from Mr Callinan were always verbal. Supt Taylor told Mr McGuinness he had been “used” by Garda management.