Fianna Fáil Senator Larry Butler has resigned the party whip after he became embroiled in controversy over expenses claims.
In a statement this evening the Senator said he had taken the action 'so as to not further distract from the important business of the Oireachtas and to deal with matters which are clearly of public concern'.
Senator Butler, who lives in Foxrock, had been asked to explain expense claims from Graiguenamanagh, Co Kilkenny.
In his statement, he insisted that he lived in Graiguenamanagh, and only stayed at his house in Foxrock on sitting days of the Seanad.
Clontarf-based Ivor Callely is also under investigation for over €80,000 worth of travel and subsistence claims from his holiday home in west Cork.
Taoiseach Brian Cowen said he was seeking the removal of the Fianna Fáil Whip from Mr Callely pending the outcome of the investigation by the Seanad's Members' Interests Committee.
He said the situation involving Senator Butler was slightly different to the controversy over Mr Callely's expenses, and he was not aware of any other Fianna Fáil parliamentarian with questions to answer about claims.
He said the Fianna Fáil party expected all these matters to be dealt with transparently, comprehensively and fully.
He added that he had not spoken to either Senator but had left the matter to Fianna Fáil General Secretary Sean Dorgan.
Meanwhile, Labour Party leader Eamon Gilmore has called for the removal of Mr Callely from the Seanad.
Speaking in Ennis this morning, Mr Gilmore said Mr Callely's explanations so far were unsatisfactory and he should go.
He said as he was the Taoiseach's nominee, it now fell to Brian Cowen to decide the Senator's future.
The Minister for Transport has urged any politician who finds themselves in difficulty with their expenses to come forward and contact the Standards in Public Offices Commission.
Speaking in Navan, Noel Dempsey said issues with politicians such as Senator Callely were emerging because of the openness and transparency within expenses system.
He said anyone with evidence or anyone who finds themselves in a situation should contact the Commission. There is, he said, no place in Fianna Fáil for anyone who abuses the system and taxpayers' money.
Fianna Fáil last night moved to expel Senator Callely from their parliamentary party.
Party Chief Whip John Curran will move a motion to that effect next week.