By Greg McKevitt
Mr Ahern told a news conference he will resign in May
Bertie Ahern oversaw a period of rapid economic growth for the Republic of Ireland, but it was questions about his own personal finances which led to his resignation as taoiseach.
In recent weeks, pressure has been mounting on him over allegations made at a judicial tribunal in Dublin investigating planning corruption.
The Mahon Tribunal is looking at lodgements of more than IR£100,000 made on behalf of Mr Ahern in the late 1980s to mid-1990s.
Last week, two cabinet colleagues went public about their concerns, saying it was time Mr Ahern addressed the disquiet felt among the public.
In announcing his resignation, Mr Ahern reiterated: "I have never received a corrupt payment and I've never done anything to dishonour any office that I've ever held."
Nicknamed the Teflon Taoiseach, allegations about Mr Ahern's finances did not affect his electoral fortunes, and last May he won a third term as taoiseach.
Since then, however, the tribunal has found that lodgements to his accounts between 1993 and 1994 were more than two-and-a-half times his salary.
It also found that he did not operate a bank account while minister for finance.
Mr Ahern said his staff cashed his pay cheques for him and either handed him cash or left bundles of up to IR£1,500 on his desk when he was away.
He also said that other money he received came from friends to help him after a marriage separation and to buy a house.
Fresh difficulties for Mr Ahern emerged last month, with evidence given to the tribunal that more than £15,000 in sterling was lodged to his account in 1994 - something which contradicted previous accounts he made to the tribunal and the media.
He says he was given £8,000 by a group of businessmen after a speaking engagement in Manchester in the 1990s.
He has vehemently challenged tribunal lawyers who have claimed he also benefited from a lodgement of £25,000, and is taking legal action in the High Court over their method of calculating this figure.
In his farewell news conference, Mr Ahern admitted "some people will feel that some aspects of my finances are unusual".
"I truly regret if this has caused any confusion or worry in people's minds," he said.