The Supreme Court has dismissed an appeal by a senior barrister against a decision upholding a challenge by former justice minister Alan Shatter to a report examining how a garda whistleblower's complaints were dealt with. 

The court found some of the report's conclusions were outside the terms of reference set down by the Government.

Mr Shatter claimed Senior Counsel Sean Guerin should have interviewed him before reaching adverse conclusions against him, in Mr Guerin's 2014 report examining how whistleblower Maurice McCabe's complaints were dealt with.  

Mr Shatter claimed the report had caused him to resign from office after it was published and his good name and reputation had been destroyed.

The High Court rejected Mr Shatter's challenge to the report but that decision was overturned by the Court of Appeal.

The Court of Appeal said Mr Guerin was obliged to observe the rules of natural justice and of letting the other side be heard.

It subsequently made a declaration that Mr Guerin's conclusions were reached in breach of fair procedures and constitutional and natural justice.

Mr Guerin then appealed to the Supreme Court. 

Giving the Supreme Court's judgment, the presiding judge, Mr Justice Donal O'Donnell, ruled that Mr Shatter was entitled to complain about the outcome of the report as it affected him. 

But he said Mr Shatter should succeed on a relatively "narrow and slender basis".

Mr Justice O'Donnell directed that the order of the Appeal Court should be substituted for a more limited declaration that some of Mr Guerin's conclusions were outside the terms of reference of his report. 

This included a conclusion by Mr Guerin that neither An Garda Síochána nor the minister seemed to have been able to "heed the voice" of Sergeant McCabe. 

A subsequent report by the Commission of Inquiry chaired by former High Court judge Mr Justice Kevin O'Higgins found Mr Shatter had acted properly at all times and cleared him of any wrongdoing in his handling of Sergeant McCabe's allegations

Mr Justice O'Donnell said he was far from being critical of Mr Guerin's role.  He said the timescale was short and there was ambiguity in the nature of the role he was asked to perform.

The judge said the difficulty of the task was compounded by a surprising lack of communication within the Department of Justice. 

The judge said a number of paragraphs of Mr Guerin's report, including the conclusion that the minister did not appear to have been able to hear the voice of a member of An Garda Síochána, such as Sergeant McCabe, were beyond the scope of the inquiry Mr Guerin was authorised to carry out.  

He said the conclusions expressed and the impression created, were damaging to Mr Shatter's reputation.

Even then, the judge ruled, if Mr Shatter had been given an opportunity to express his views and have them reflected in the report, he did not think Mr Shatter could have complained or a court could have intervened. 

But Mr Justice O'Donnell said this step was not taken.