Fianna Fáil leader Micheál Martin has expressed deep concern about the administration of justice in the State, claiming he has documents which show that cases of “abduction, assault and ultimately murder” have not been properly investigated.

Mr Martin said Minister for Justice Alan Shatter had failed to take action to investigate the claims and a commission of inquiry was now required. He said the Minister’s position was no longer tenable.

Mr Martin received documents relating to nine cases from Garda whistleblower Sgt Maurice McCabe during a three-hour meeting in Portlaoise last Friday.

“I have sent material to the Taoiseach in relation to other issues the whistleblower has raised, pertaining to issues outside of the penalty points dossier, which relate to the failure to fulfil basic functions in terms of a range of cases – very, very serious cases – involving abduction, assault and ultimately murder, which leaves huge questions for response,” he told reporters at Leinster House.

He said the material given to him by Sgt McCabe related to some cases that have been in the public domain. One of them relates to the murder of Sylvia Roche Kelly, who was found dead in the Clarion Hotel in Limerick in December 2007.

Mr Martin said the files detailed the circumstances surrounding assaults and murders, how they were dealt with and the consequences for the victims over a number of years.

He said Mr Shatter should correct the public record and acknowledge that Sgt McCabe attempted to co-operate with a Garda internal investigation into the penalty points controversy, as well as apologise to the sergeant himself.

Earlier in the Dáil Mr Martin said the matter must be taken out of the hands of the Department of Justice in order to get to the truth.

“They are shocking revelations of incompetence which ultimately led to people being murdered as a result of a failure to act. It is very serious stuff which the Department of Justice and Equality has had for quite a long time but not acted on.”

Mr Martin’s allegations came on a day when Mr Shatter was under siege on a number of fronts.

It emerged in the Dáil that the Minister had relieved Garda confidential whistleblower liaison official Oliver Connolly of his duties.

The move followed claims from Independent TD Mick Wallace and Mr Martin that Mr Connolly had had an inappropriate conversation with Sgt McCabe.

Both TDs had recently read extracts from a tape recording of a conversation involving Mr Connolly and Sgt McCabe into the record of the Dáil.

Mr Connolly was appointed by Mr Shatter in June of 2011 to be the point of contact for whistleblowers within the Garda.

One of the extracts read into the record by Mr Martin said: “If stuff was to get out into the public, the print media, I tell you something Maurice – and this is just personal advice to you – if Shatter thinks you’re screwing him, you’re finished.”

Last night Mr Shatter in evidence to the Oireachtas Committee on Public Service Oversight expressed doubt about the basis on which the Garda Síochána Ombudsman Commission (GSOC) began an investigation into suspected surveillance at its offices. The Minister said it was not a proportional response and was based on “feelings”, not evidence.