The President of the Garda Representative Association (GRA) said many of his 11,550 members had lost confidence in the Garda Siochana Ombudsman Commission (GSOC) and levels of trust were decreasing.

Damien McCarthy said that hundreds of complaints to GSOC about members of the force were dismissed every year, but just one member of the public had been convicted for making misleading statements about Gardaí.

"From what I'm hearing, confidence has decreased," McCarthy said, adding that he "found it hard to believe" there had been just one conviction for a malicious complaint to GSOC.

Last week, two former Gardaí were sent to jail in Waterford after GSOCC secured its first convictions in a jury trial. GSOC said the case should send a "message" that juries and courts would not tolerate criminal misbehaviour from Gardaí.

McCarthy did not want to speak about the case other than to say he believed the comments made by GSOC were not "necessary''.

McCarthy said Gardaí were alarmed at what they believed was threatening behaviour by GSOC investigators during the prosecution of a garda for assault last February. Garda Brendan Whitty was found not guilty of assault after he used his baton to subdue a man. During the trial GSOC investigators rang a garda witness to seek extra information after the judge questioned evidence.

A recording of a voicemail left on the garda's phone was played to the Sunday Times.

The GSOC investigator, who was seeking clarification of evidence the garda had given, asks him to return the call, and then there is a long pause during which a second person can be heard whispering.

The investigator then says: "If we haven't heard from you within the next hour or so of this call, we will deem it a refusal to comply and we will have to report it to the DPP [Director of Public Prosecutions] tomorrow morning. Thanks very much."

McCarthy said the garda, who was of "very junior experience", called him in a distressed state when he received the message after the one-hour deadline. "He was out walking the dog, off duty, and only heard the message that night and was seriously distressed by it," said McCarthy. "He thought he had done something wrong and I had to reassure him that he hadn't as he'd co-operated fu11y with the investigation."

He said concerns about this incident and others "dealt a serious blow" to the confidence of Gardaí in the ombudsman.

Regarding the complaint about the voicemail, Kieran Fitzgerald, a GSOC spokesman, said he didn't think "discussing in isolation one element of a complicated situation is of benefit to anyone.