The Garda Commissioner is facing renewed calls to stand aside while a tribunal of inquiry into the garda whistleblower scandal is underway.

The Charleton tribunal is due to begin its work on Monday in Dublin Castle - just 11 days after its terms of reference were passed by the Dáil and the Seanad.

The inquiry has been set up to look into allegations made by Superintendent Dave Taylor, the former head of the Garda press office, who says he was instructed by senior officers to smear the Garda whistleblower Maurice McCabe.

It will also examine the circumstances of the Tusla file created against him - which carried false allegations of sex abuse against McCabe.

Commissioner O’Sullivan has insisted she had no knowledge of the alleged campaign and refuted “in the strongest terms” allegations that she phoned journalists to make them aware of false claims of sexual abuse made against Sergeant McCabe.

Speaking today the chairperson of the Policing Authority Josephine Feehily said she has a degree of confidence in the in Commissioner Nóirín O'Sullivan - but added that she is concerned about her ability to carry out her role while the tribunal is ongoing.

Meanwhile the Minister for Transport, Shane Ross has reportedly called for an independent review of how the force operates – before the tribunal completes its work.

Sinn Féin Justice spokesperson Jonathan O'Brien has again called for the commissioner to stand aside and speaking to Newstalk Drive this evening, Sinn Féin senator Pádraig Mac Lochlainn echoed that standpoint:

“For somebody with such profound responsibilities to our people and to government to be at the helm while all this is happening - and we are talking here about very, very serious matters  - I think that while all of that is being investigated without prejudice the Garda Commissioner needs to step aside,” he said.

The opening statement from the chairman of the Charleton Tribunal is expected to be televised on Monday – however the cameras will be removed when witnesses are giving evidence.