The Director of Communications for An Garda Síochána, Andrew McLindon, has denied knowledge of a senior garda smear campaign against Sergeant Maurice McCabe.

The Disclosures Tribunal heard that former garda press officer, Superintendent Dave Taylor, said Mr McLindon was aware of such a campaign.

Mr McLindon said he was not aware of negative briefings on Sgt McCabe and he said he would have been absolutely appalled if that was the attitude adopted by the Garda Commissioner.

Supt Taylor's lawyer, Michael O'Higgins, said that he would give evidence that Mr McLindon was not present when former Commissioner Martin Callinan gave Supt Taylor instructions on the sergeant but that Supt Taylor would then inform Mr McLindon.

Mr McLindon said that was not true. He said Supt Taylor was the main conduit to Mr Callinan.

Mr O'Higgins said Supt Taylor told Mr McLindon in categoric terms that the Garda Commissioner had instructed him to draw journalists' attention to the allegation of sexual assault made against Sgt McCabe, the garda investigation and that Sgt McCabe was disillusioned and embittered and that was partly driving his agenda.

Mr McLindon said that did not happen and he said he would have been appalled and highly concerned if he had heard that.

Mr McLindon also told the Tribunal that he was shocked and concerned when he heard Mr Callinan refer to the actions of whistleblowers as disgusting. Mr Callinan made the comments at the Public Accounts Committee on 23 January 2014.

Mr McLindon said they had done a lot of preparation for the Committee and that approach was never discussed. He said it was a very strong term.

He said he would have spoken to Mr Callinan about it but there was no opportunity as the hearing continued for five hours without a break.

Mr McLindon said he felt the comment was undermining the Commissioner's position and the organisation, and he proposed Mr Callinan withdraw it or move off it during a radio interview.

He said Mr Callinan rejected the proposal and was not prepared to change his position.

The Tribunal was also shown his note of a meeting on 21 January 2014 in Garda Headquarters, called to prepare for the Public Accounts Committee. It referred to "2006 first incident Sgt serving".

Mr McLindon agreed this probably referred to the 2006 Ms D allegation made against Sgt McCabe.

Mr Justice Peter Charleton said he was mystified as to why the issue was on the table at all given that the DPP had said that even if what was described had occurred, that it did not constitute a crime.

Earlier today, the Comptroller and Auditor General said that Mr Callinan told him that Sgt McCabe was not to be trusted, had questions to answer and that there were sexual offence allegations against the sergeant.

Seamus McCarthy said the comments were made to him just before Mr Callinan's appearance at the Public Accounts Committee on 23 January 2014.

Mr Callinan denies making the remarks.

Mr McCarthy said he was surprised and he initially thought Mr Callinan was referring to a paedophile case where Sgt McCabe was accused but later cleared in relation to a missing computer.

He said his immediate concern was the mention of the sergeant's name as the whistleblower's role in passing on information to the C&AG had never been shared with An Garda Síochána.

He said he responded to Mr Callinan that his report on penalty points was not based on information from whistleblowers, but was instead based on a random sample.

Under cross-examination by lawyers for Mr Callinan, Mr McCarthy said he did not make a contemporaneous note of the conversation and he did not tell anyone at the time.

The tribunal heard that nobody else was within earshot at the time.

Conor Dignam SC, for Mr Callinan, said the former commissioner's evidence would be that he mentioned "question" in the context of some of the sergeant's allegations on penalty points being questionable.

He also said that Mr Callinan would say that it was Mr McCarthy who raised sexual offence allegations.

Mr McCarthy said that was not correct.

Mr Dignam suggested to Mr McCarthy that he was not entirely clear on what was said by Mr Callinan.

Mr McCarthy replied: "I think I am."