The garda whistleblower Maurice McCabe is denying that the Garda Commissioner wrote to him and told him to co-operate with the garda investigation into the cancellation of penalty points.

In a statement tonight Maurice McCabe vehemently denies he was ever asked to cooperate with an inquiry into the penalty points issue by Assistant Commissioner John O'Mahony.

Sergeant McCabe says he was never contacted by the inquiry to give evidence.

He claims that on the 14th December 2012 he was given verbal instructions from a Chief Superintendant - which came directly from the Garda Commissioner.

Sergeant McCabe says the direction was for him to desist from the accessing the Pulse system - and disclosing data on the cancellation of penalty points by gardai to a third party.

The direction said if Segeant McCabe had any further concerns about the matter he should bring them to the attention of John O'Mahony.

Maurice Mc Cabe said when he learnt the O'Mahony inquiry had proceeded without him, he protested at what had happened.

Earlier this evening, Sinn Fein called  for Justice Minister Alan Shatter to appear before the Oireachtas Justice Committee this week.

Deputy Padraig MacLochlainn has written to the Committee chairman, requesting that an invitation be sent to him.

He says Minister Shatter has questions to answer after a dossier containing further garda whistleblower claims was given to the Taoiseach.

Padraig McLochlann says a lot of questions remain unanswered.

The Fianna Fail leader revealed earlier that he was contacted by another garda whistleblower.

Micheal Martin says he met with him and was handed a dossier about a murder case which the man alleged was not properly dealt with.

He has also confirmed he has been in contact with a female whistleblower in the force who was the subject of newspaper reports at the weekend.

Fianna Fail says any additional information they get in relation to whistleblowing in the gardai will be passed on to the Taoiseach.

Deputy Martin said earlier the man who contacted him was prompted to do so by media reports, but is unable to comment publicly on his experience.

Earlier today the Tánaiste Eamon Gilmore and Minister for Communications Pat Rabbitte said they have full confidence in the Minister for Justice.

But Mr. Gilmore says issues of possible garda misconduct raised by the Fianna Fáil leader Micheal Martin need to be looked into.

The handling by Alan Shatter of the allegations has come under scrutiny after it emerged that he was made aware of the claims two years ago.

The Tanaiste says the government wants to strengthen protection for whistleblowers, but that Alan Shatter enjoys his full confidence.

While Minister Pat Rabbitte says he expects Alan Shatter will report to Cabinet tomorrow on the controversy involving Sergeant McCabe.

The Minister says time is needed to establish all the facts.