The Disclosures Tribunal has found there was "a campaign of calumny" against garda whistleblower Sergeant Maurice McCabe by Commissioner Martin Callinan and he was actively aided by his press officer Superintendent David Taylor.

The Disclosures Tribunal's third interim report was published today.

It says Mr Callinan went on a "frontal attack" denigrating the character of Sgt McCabe by making derogatory comments to several individuals about the sergeant.

Mr Callinan had denied making the remarks around the time of the Public Accounts Committee's investigations into penalty points in January 2014, however Mr Justice Charleton has found against him on the evidence of four individuals.

John McGuinness TD, John Deasy TD, Comptroller & Auditor General Seamus McCarthy and RTÉ broadcaster Philip Boucher-Hayes all gave evidence that Mr Callinan had told them that Sgt McCabe was not to be believed or trusted and had sexual offences allegations against him.

Mr McGuinness had also said that Mr Callinan told him that the sergeant had abused members of his own family.

Mr Charleton had found that all four were telling the truth.

He said Mr McGuinness had genuine recall and the conversations he cited had taken place. 

Mr McCarthy was accurate, Mr Deasy was correct and Mr Boucher-Hayes was telling the truth.

Mr Charleton said that the former commissioner's state of emotion left him in a position where only a frontal attack would head off what he saw as an undermining of standards of duty and loyalty to which he had devoted his career.