The Gardaí has been accused of bad policing in dozens of investigations into murders, abductions and assaults.

In an extraordinary allegation of rogue policing and cover-ups, Taoiseach Enda Kenny has been handed a dossier claiming scores of serious crimes were not properly investigated over several years.

Opposition leader Micheal Martin made the damning claims – including some cases which have already been made public – after seeing a sample of 10 cases and meeting Garda whistleblower Sergeant Maurice McCabe.

One of the cases relates to the killing of 33-year-old Silvia Roche Kelly in the Clarion Hotel in Limerick in December 2007.

Jerry McGrath, from Dundrum, Co Tipperary was jailed for life for her murder in 2009. At the time he had been on bail after being charged with attempting to abduct a five-year-old girl from her bedroom and months before that had been charged with assaulting a middle-aged female taxi driver in Co Meath.

Mr Martin said the documents he has seen involved inadequate policing and failures to fulfil basic duties which led to murder, abduction and assaults.

The opposition chief said attempts were also made to bury the allegations in confidential court settlements and demanded the Taoiseach set up a commission of inquiry into the allegations.

“These assertions have been made. There’s a document there. I’m saying it needs to be investigated,” he said.

The allegations are the latest in a series of controversies to hit the Garda, Justice Minister Alan shatter and the Government following claim and counter claim over suspicions of a surveillance operation at the Garda Síochána Ombudsman Commission (GSOC) and the penalty points scandal.

Whistleblower Sgt McCabe is understood to have spoken to a number of TDs about his claims over the last number of months and years.

In the last month he also gave evidence in private to a parliamentary committee over alleged Garda abuse of the fixed charge notice system for driving offences.

Mr Martin said the material compiled by the Garda whistleblower includes the circumstances around the murders, assaults and abductions, how the cases were dealt with and the consequences for victims.

“There’s a whole series of events there and omissions that need to be investigated and in my view need to be publicly aired,” he said.

“It needs to be investigated... not with a view to go after people. It’s with a view to assure public confidence in the administration of justice.”

Sgt McCabe has been pursuing allegations of corruption and bad policing among some officers in the Cavan-Monaghan region for a number of years and claims that none of his reports have been properly investigated despite going through the Garda confidential recipient.

The lawyer who acted as that official liaison, Oliver Connolly, has been sacked, it was announced today.

The Taoiseach said he had been relieved of his duties after a transcript of a conversation he had with Sgt McCabe was leaked out showing him warning the whistleblower not to pursue cases of rogue policing or cases against the Justice Minister.

Mr Martin said he does not believe Mr Shatter’s position is tenable, but stopped short of calling on him to resign.

The GSOC last year launched an investigation into an allegation of a cover-up within the force over Ms Roche Kelly’s murder and the fact that the killer was on bail for serious violent charges at the time.