The Garda Commissioner has said a criminal investigation was carried out into the alleged cancellation of penalty points before an assistant commissioner was assigned to investigate the whole matter.

A file in relation to one member of the gardaí has been sent to the Director of Public Prosecutions in relation to that investigation.

She will decide if criminal charges are to be preferred.

Assistant Commissioner John O’Mahony's report found no evidence of criminality or corruption, but three officers are facing disciplinary proceedings.

Commissioner Martin Callinan also said he was not aware that former garda John Wilson was a whistleblower until he was informed that Mr Wilson had printed documents from the pulse computer system to hand over to a politician.

Mr Wilson said this evening he was making no comment on the commissioner's statement.

He has already said he contacted independent TD Clare Daly after he felt his complaints were not being dealt with.

Commissioner Callinan also confirmed that penalty points were cancelled for him personally after he had been caught speeding.

However, he insisted that he was on duty at the time, he was entitled to have the points cancelled and there was a proper audit trail.

Earlier, Commissioner Callinan strongly defended the senior officers who conducted the investigation.

He told the Public Accounts Committee that the allegations were very disturbing, but he was satisfied that no stone had been left unturned.

He said three officers are now facing a disciplinary inquiry and these were extremely serious matters.

The commissioner said having looked at the cases concerned he would not have agreed with some of them.

He said there was an issue with the retention of paperwork and greater oversight.

A directive has been sent out to all officers who can cancel fixed penalty point notices reminding them of the process.

Asked about criticism by the Garda Síochána Ombudsman Commission of the delay investigating alleged collusion with convicted drug trafficker, Kieran Boylan, Commissioner Callinan said there was very substantial co-operation with that investigation.

He said reassurances were needed to ensure that information about garda informants would not leak out which could put lives in danger.

Fine Gael's John Deasy asked whether the rules of engagement had been broken in the Boylan case.

Commissioner Callinan said that his views were known and he did not want to comment on particular cases but that people should not be allowed to engage in criminal activity.

He said that informants are extremely difficult to handle and gardaí have to walk a very fine line.

The commissioner said that handlers have to keep notes and are not allowed to engage in criminality.

He added that gardaí have been in contact with the Ombudsman's office to discuss how to handle and pass on information gleaned via informants.