Opposition TDs walked out of the Dáil in a row over the ruling out of a debate on a motion setting up a commission of investigation into claims of Garda malpractice.

Ceann Comhairle Sean Barrett ruled earlier this week that the matter could not be debated because it was sub judice and would contravene the Dáil’s standing orders.

Before Wednesday’s walkout, Taoiseach Enda Kenny said a ruling made by the Ceann Comhairle was not reversible. “The Ceann Comhairle, in his utter independence, has made a ruling that a debate is not allowed,’’ he added.

The commission is to investigate allegations of malpractice in the Cavan-Monaghan division of An Garda Siochana and follows the findings of a report by Sean Guerin SC into claims made by whistleblower Maurice McCabe.

Mr Guerin's report led to the resignation of Fine Gael TD Alan Shatter as minister for justice.

When the vote was called today, TDs on the Opposition benches left the chamber. A note issued to TDs by Mr Barrett’s office on Tuesday indicated that while the motion could be moved today, there could be no debate as it was currently sub judice.

This is understood to refer to a High Court action taken by Mr Shatter to overturn some of Mr Guerin's findings.