The head of security of the horse racing regulatory body, the Turf Club, claims he was defamed in a letter about his role in an inspection of trainer Liz Doyle's yard.
Chris Gordon (60) is suing the Irish Racehorse Trainers Association (IRTA) over a letter to a senior Turf Club steward, in which he says it was falsely alleged Mr Gordon tried to entrap Ms Doyle into an admission of wrongdoing.
The court heard the letter arose after Ms Doyle's yard at Kitestown House, Co Wexford, was inspected in March 2014 by Department of Agriculture and Turf Club officials.
This was part of an investigation related to the use of performance enhancing drugs in racehorses.
Ms Doyle is a daughter of former Fine Gael MEP Avril Doyle, who was also present in the yard during the inspection.
In High Court proceedings, Mr Gordon also claims he was further defamed when the IRTA chairman Noel Meade, in an interview with the 'Irish Field' in August 2014, said members were angered by the conduct of some officials during inspections carried out at horse trainers' premises as part of this investigation.
Mr Meade claimed there was a "little Hitler syndrome" where trainers were treated almost as guilty from the start and that they didn't like being "treated like criminals".
Mr Gordon, a former garda superintendent, claims he was further defamed when the IRTA published a petition to its members seeking to have him removed as security chief on grounds of misconduct.
It is also alleged IRTA committee member Michael Grassick made false claims about Mr Gordon's conduct during inspections of two other trainers' premises.
It is also claimed Mr Meade, Mr Grassick and another IRTA committee member, Michael Halford, met with representatives of the Turf Club and maliciously published statements seeking Mr Gordon's removal.
Mr Gordon says as a result the Turf Club held an inquiry which concluded Mr Gordon had done nothing wrong.
He claims the allegations were made with malice and meant, among other things, he engaged in unprofessional behaviour, corrupt practices and abused his position.
The IRTA denies the claims. It also pleads qualified privilege which protects a statement published to someone with an interest in receiving such information as long as it is not motivated by malice.
Opening the case, Tom Hogan SC said the inspection of Ms Doyle's yard was the first of a number after the Turf Club and Department of Agriculture decided to share intelligence to carry out investigations into the use of anabolic steroids in the industry.
It followed the conviction in 2013 of John Hughes, a retired department vet, for possession of 6kg of Nitrotain.
Using the book of evidence in that case, Turf Club and department officials went over a number of documents provided by Hughes.
The trial continues.