The present system for investigating allegations of Garda wrongdoing was "not fit for purpose" and contained significant legal risks, according to the lawyer for a high-profile whistleblower.

Speaking on RTÉ's This Week programme, Trevor Collins, solicitor for Garda whistleblower Keith Harrison, said that investigations by the Garda Síochana Ombudsman Commission were at the mercy of "if and when" gardaí would hand over key files in relation to complaints.

He said it was "simply unacceptable" that two years had passed since his client first made a protected disclosure to GSOC, and the Garda Ombudsman had informed him they were still waiting for documents from gardaí to process the case.

"My experience on behalf of my client is one of frustration" said Mr Collins, solicitor with Kilfeather and Company.

Gda Harrison has claimed that he was subject to mistreatment with the force after arresting another garda for suspected drink-driving.

Gda Harrison's solicitor told RTÉ that his client has provided all the information required of him for some time, but that due to what GSOC described as a "delay" on the garda side, his client has been "left in limbo for two years".

Gda Harrison first raised his concerns with the official confidential recipient over two and a half years ago, and later brought his concerns to GSOC under a protected disclosure.

Mr Collins warned that there were considerable legal risks to all sides if delays mounted up in serious investigations.

Such a delay was "prejudicial to the complainant and the person who is the subject of the complaint," prompting a fear that any garda found to have committed wrongdoing could apply to have the finding quashed or the process stopped due to a failure to inordinate delay.

He said it was essential that GSOC be given the power to go to the High Court and compel gardaí to hand over files relating to investigations if they felt that material was not being provided with sufficient haste, echoing comments by the chairperson of GSOC, Judge Mary Ellen Ring, who last month told the Oireachtas Committee on Justice that delays in handing the information need to be addressed by legislation.

Meanwhile, the chairman of that committee, Caoimhghin Ó Caoláin, has said that it would be "very important" for Minister for Justice Frances Fitzgerald to make public a report which has been sent to her, into issues relating to the treatment of Garda whistleblower Sergeant Maurice McCabe.

RTÉ's This Week programme revealed last month that a report had been sent to the Minister for Justice by the Garda Commissioner Nóirín O'Sullivan, on recommendation by the report's author John Barrett, who is the civilian head of human resources in An Garda Síochána and who liaised with Sgt McCabe.

The report concerns matters relating to the treatment of Sgt McCabe, who raised multiple issues relating to alleged garda wrongdoing, ultimately leading to a report by the Garda Inspectorate into penalty points abuses and the establishment of the O'Higgins Inquiry into allegations of malpractice in certain criminal investigations.

A spokesman for the Minister said that there was "ongoing correspondence" between the Department and garda authorities in relation to the matter and that due to legal issues and the right to confidentiality of persons named in the report, it would not be possible to put any further information into the public domain at present.