A senior garda officer has written to the Office of the Data Protection Commissioner over Nóirín O'Sullivan's use of her private gmail account for official business, the Irish Independent has learned.
The high-ranking garda is understood to have sought information over whether an internal promotion process, in which he was involved, was discussed in correspondence sent by the Garda Commissioner from her private account.
Commissioner O'Sullivan faced criticism in November after it emerged she sent potentially sensitive information via the commercial email service.
Gardaí subsequently began the process of trawling through six years of her emails to ensure her account had not been hacked.
But the latest development involving the senior officer and his decision to directly contact the Data Protection Commissioner will be viewed as significant. An Garda Síochána refused to comment on the issue.
However, a Garda spokesman insisted that there was "no evidence" any devices issued to the commissioner had been compromised.
"An Garda Síochána has strict security controls in relation to the use and access to Garda IT systems. Devices issued to the commissioner are secured by secure connections and utilise strong encryption technologies. Access to the PULSE database on any Garda Síochána devices is segregated by secure containers which does not store any Garda data on the device. This is coupled with strong users password policies and strong authentication," the spokesman told the Irish Independent.
"The commissioner is well aware of her obligations to protect national security and policing operations and would under no circumstances allow them to be compromised."
The officer in question who contacted the Data Protection Commissioner is of very senior rank and highly respected within the force.
The move, however, is another illustration of the tensions that exist between Commissioner O'Sullivan and some of her senior colleagues within the force.
As previously reported by this newspaper, a number of senior civilian officers recently wrote to the Deputy Garda Commissioner Donal Ó Cualáin following the introduction of a series of new controls introduced in Garda headquarters.
Senior civilians said they felt isolated and of the view that their roles had been seriously diminished as a result of the changes brought in by Commissioner O'Sullivan.
Then, in October, Commissioner O'Sullivan was openly challenged at a meeting of her senior management team after she proposed to "name and shame" under-performing Garda districts at an upcoming summit of superintendents.
However, one of her greatest challenges lies ahead in 2017. Tánaiste and Justice Minister Frances Fitzgerald is preparing to publish a report by retired judge Iarfhlaith O'Neill which has examined allegations of a smear campaign against garda whistleblowers.
The report is expected to recommend a commission of inquiry. Ministers believe that Commissioner O'Sullivan may come under pressure to step aside, at least on a temporary basis, if an inquiry is set up by the Government.