Former Garda press officer Superintendent David Taylor is suing Garda Commissioner Nóirín O'Sullivan and the State for damages arising out of his suspension and arrest over alleged leaks to journalists.
The officer is seeking compensation after he was suspended for 22 months while an investigation took place, during which time his pay was reduced.
It is understood issues relating to his arrest and detention also form part of the case, which was initiated in the High Court earlier this week.
Supt Taylor was held for 21 hours at Balbriggan garda station as part of the probe.
While suspended, he made protected disclosures to Justice Minister Frances Fitzgerald alleging he was directed by senior gardaí to spread malicious rumours about whistleblower Sgt Maurice McCabe and that Commissioner O'Sullivan had knowledge of the smear campaign. This has been denied by the commissioner.
The allegations proved to be a major catalyst for the setting up of the Disclosures Tribunal.
Supt Taylor had been attached to the traffic unit at Dublin Castle when he was suspended, and he returned to work there last month after the DPP found there were no grounds for a prosecution.
Two lawsuits were issued by Supt Taylor's legal representative, ME Hanahoe Solicitors, on Tuesday.
One is a personal injuries claim seeking damages, with Commissioner O'Sullivan, the Attorney General and the State named as defendants. The other case is seeking a number of declarations, with the Justice Minister added as an additional defendant in that action.
Supt Taylor was suspended as part of an investigation into alleged leaks of information relating to the Roma children controversy in 2013.
Two children were temporarily removed from their families in Tallaght and Athlone amid unfounded concerns they were not living with their biological parents.
Supt Taylor was Garda press officer at the time and has denied acting inappropriately.
A report on the cases by then-Ombudsman for Children Emily Logan found that sensitive information regarding the Tallaght child entered the media inappropriately and that, on the balance of probabilities, the information came from someone with the gardaí.
While Supt Taylor was suspended, his pay was reduced at one stage by 25pc, but the money is due to be repaid to him.
The garda investigation was led by Chief Supt Frank Clerkin and Detective Supt James McGowan, who is Ms O'Sullivan's husband.
Supt Taylor's legal action comes just a week after Sgt McCabe issued proceedings seeking damages against Ms O'Sullivan and her predecessor Martin Callinan.
Sgt McCabe has also filed separate damages claims against Tusla and the HSE, arising out of the creation of a file containing false sexual abuse allegations against him.
The Disclosures Tribunal is to probe whether or not Supt Taylor was instructed by Mr Callinan and/or Ms O'Sullivan to contact the media to brief them negatively against Sgt McCabe after he raised concerns about abuse of the penalty points system.