A trawl by the Department of Justice has revealed that the then Garda Commissioner Noirín O'Sullivan personally told a senior official at the Department of Justice about the legal dispute which arose at the O'Higgins Commission, in which her legal team challenged the motivation of garda whistleblower Sgt Maurice McCabe, RTE's This Week programme has learned.

It is the first time that any indication has emerged that the Garda Commissioner personally contacted the Department to discuss aspects of the controversial strategy to challenge Mr McCabe's motives at the Tribunal in May 2015.

The Department of Justice has confirmed to RTÉ that the contact took place.

However, sources say that Tánaiste Frances Fitzgerald was not told of the conversation between Ms O'Sullivan and a senior official at the Dept of Justice.

The Departmentsaid the conversation occurred "at the time" of the legal dispute in the Tribunal, but said they had no written record or otherwise and could say no more due to the upcoming Disclosures Tribunal.

It is the second verifiable instance in which the Department, then headed by Ms Fitzgerald, was told about aspects of the controversial legal strategy before it became public the following year.

It later publically emerged in May 2016 that Ms O'Sullivan had instructed her legal team to challenge Mr McCabe's motivation for raising concerns about wrongdoing in the force.

After the legal strategy to attack Mr McCabe's motivation became known, Ms Fitzgerald, who was Minister for Justice at the time, said on the Dáil record in May 2016 that she had no knowledge of the attack on