Garda whistleblower Keith Harrison's solicitor has said his client has had to endure a campaign to undermine his credibility that he believes was orchestrated by senior members of An Garda Síochána since he made a protected disclosure over two years ago.

Trevor Collins said that they have made Tánaiste and Minister for Justice Frances Fitzgerald aware of this ongoing campaign and called on her to take action.

The minister last week asked a retired High Court judge to examine allegations of wrongdoing contained in protected disclosures made by Garda whistleblowers.

Mr Justice Iarfhlaith O'Neill has been asked to review allegations of wrongdoing contained in the disclosures and to make any inquiries with persons or bodies that he considers appropriate in relation to the review.

He has also been asked to report within six weeks on the conclusion of the review.

Speaking on RTÉ's Morning Ireland, Mr Collins said Garda Harrison "has been the subject of surveillance. He has suffered victimisation, bullying and harassment, as has his family.

"There has been a decimation of rumour and innuendo which has been solely designed to undermine his credibility and that has been circulated within certain members of the media, certain politicians and his Garda colleagues.

"And furthermore there has been a deliberate frustration of GSOC'S investigation of his disclosures."

He said that his client was "astounded" to learn the terms of reference on Friday evening.

Mr Collins said that it was disappointing to learn that the Minister for Justice had chosen to base any inquiry solely upon the disclosures of Sergeant Maurice McCabe and Superintendent David Taylor, rather than the other whistleblowers who have suffered similar treatment.

He added that his client has made the serious issues he has suffered known to Ms Fitzgerald and they have outlined the issues of public concern.

Mr Collins said that to simply ignore these issues and leave his client in limbo does not "vindicate his rights".

The scope of the inquiry has to be widened, at the very least, to include all whistleblowers who have brought matters of ill-treatment to the attention of the Minister for Justice, he said.

He added he would have to reserve his position on the terms of reference and power on Mr Justice O'Neill.

Meanwhile, Fianna Fáil's Justice Spokesman has said the terms of reference of the inquiry should be broadened to include allegations from Garda Harrison and Garda Nicky Keogh.

Speaking to RTÉ’s News at One, Jim O'Callaghan said: "If we are now going to have an inquiry into whistleblower allegations then it makes sense that all of them be put together in the one inquiry."

Mr O’Callaghan said including the allegations by the two gardaí would lengthen the inquiry, however excluding them would mean the claims would be left "festering" and "left over people and I think we are better off dealing with them all by Judge O'Neil".