Senator Ivor Callely has resigned the Fianna Fáil party whip with immediate effect.
In a statement, issued this afternoon, Senator Callely apologised for the controversy he had generated and how that has impacted on the members of the Oireachtas and politics in general.
Mr Callelly said: 'I deeply regret that the statement I made in Seanad Éireann on Wednesday was not sufficient and with hindsight I would have handled that opportunity differently. I did not furnish enough information and I apologise for that'.
The statement from Senator Callely comes after several days of sustained criticisms arising from the disclosure that he claimed over €80,000 in expenses over a two-year period.
He insisted that when he was appointed to the Seanad by Bertie Ahern he was living in West Cork and his expenses claims were initiated as he put it to reflect that position.
Mr Callelly said he understood the public anger over the situation and was sorry if his actions had made the last week difficult for his family friends and supporters.
He is resigning the party whip without prejudice to the ongoing investigation into his affairs by the Seanad Members' Interests Committee.
Last night, Senator Larry Butler, whose expenses are also under scrutiny, resigned from the Fianna Fáil parliamentary party.
Mr Butler had claimed expenses from Graiguenamanagh, Co Kilkenny, but was resident in Foxrock in south Dublin when he was elected to the Seanad.
In a statement last night, he said he subsequently moved to Graiguenamanagh and had intended to sell his Foxrock home were it not for the property slump.
He said his practice was to stay there during sitting days of the Seanad and this might have given rise to ill founded rumours about his expenses.
Notwithstanding these, he said he had told Taoiseach Brian Cowen he was resigning the Fianna Fáil parliamentary party whip and would deal with the matter with the members' interests committee where he was confident his name would be cleared.