Timeline of the whistleblower crisis
January 2012: Mr Shatter receives report from Garda Confidential Recipient Oliver Connolly detailing allegations of garda misconduct from Sergeant Maurice McCabe
November 28-29, 2012: A series of articles in the Irish Independent first revealed claims that well-known individuals, including a sports star and judges, had had their penalty points cancelled
December 2012: Independent TDs name judges who had penalty points wiped from their licences under Dail privilege.
May 2013: Garda internal review of points systems leads to disciplinary proceedings for three gardai, and changes to system.
June 2013: Transport Minister Leo Varadkar says he met Sgt McCabe and found him "credible".
September 2013: Comptroller and Auditor General finds significant failings in points system which are losing the State millions of euro.
December 2013: Sgt McCabe sends Oireachtas Public Accounts Committee box of evidence detailing terminated penalty points. Garda Commissioner Martin Callinan says information should be returned to his office, and threatens legal action.
January 23, 2014: Mr Callinan appears before the PAC and describes the actions of Sgt McCabe and retired garda John Wilson as "quite disgusting".
January 30, 2014: Sgt McCabe gives evidence in private to the PAC.
February 5, 2014: Independent TD Mick Wallace (pictured) reads a transcript of conversation between confidential recipient Mr Connolly and Sgt McCabe into the Dail. Mr Connolly allegedly tells Sgt McCabe that Mr Shatter would "go after" him if his complaint became public knowledge.
February 19, 2014: Mr Connolly is sacked from his position and Mr Shatter announces reforms of whistleblower system.
March 12, 2014: Garda Inspectorate finds widespread breaches of penalty points system. Chief Inspector Bob Olson describes Sgt McCabe as credible. Garda Commissioner releases statement clarifying his use of the word "disgusting", saying it was not about character of whistleblowers but rather how confidential information made it into the public domain.
March 20, 2014: Mr Varadkar calls on Mr Callinan to withdraw his "disgusting" remark. Labour ministers back his call.
March 24, 2014: The Government prepares for a crunch cabinet meeting. Mr Callinan stands his ground as Labour shies away from putting further pressure on him.
March 25, 2014: The Garda Commssioner Martin Callinan resigns