DUBLIN — Prime Minister Bertie Ahern of Ireland, one of Europe’s longest-serving leaders, who was closely involved in the negotiations that brought peace to Northern Ireland, announced Wednesday that he would resign next month.

He denied accusations of corruption in the 1990s, when he was finance minister, but said he was quitting to prevent his government’s work from being “constantly deflected by the minutiae of my life, my lifestyle and my finances.” He forecast that a tribunal investigating payments received by Irish politicians would find that he had not acted improperly.

In emotional tones at a hastily convened news conference here, Mr. Ahern, 56, said he would quit on May 6. A week before that, he is to address both houses of Congress in Washington.

The announcement Wednesday sealed a reversal of fortunes for a man once nicknamed the Teflon Taoiseach — the Irish word for leader or prime minister — for his ability to survive onslaughts by political foes.

During Mr. Ahern’s 11 years in office, Ireland’s economy has undergone a transformation to become one of the most robust in Europe, though more recently, economic growth has slowed.

His planned resignation raised questions about the future of his coalition government and about his ambitions. Supporters hint at his possibly becoming the first permanent president of the European Union, a new role being proposed for the 27-nation bloc.

“Ahern likes Europe,” said Sean Donnelly, a leading pollster who has worked for Mr. Ahern. “He is not just going to walk away from politics.”

Other analysts, however, said Mr. Ahern’s prospects would depend on the outcome of the tribunal investigating accusations that Irish politicians received payments from real estate developers in return for favorable planning decisions. It is called the Mahon Tribunal after Alan Mahon, a judge who leads it.

“I want everyone to understand one truth above all else,” Mr. Ahern said Wednesday. “Never, in all the time I have served in public office, have I put my personal interest ahead of the public good.”

He went on: “While I will be the first to admit that I have made mistakes in my life and my career, one mistake I have never made is to enrich myself by misusing the trust of the people. I have never received a corrupt payment, and I have never done anything to dishonor any office I have held.”

The leader of the centrist Fianna Fail party, Mr. Ahern was re-elected last June for a third term in office, which was to last until 2012. At that time, he said he would not serve the full term.

At the news conference, Mr. Ahern said of the accusations against him, “All of these issues arose in a period when my family, personal and professional situations were rapidly changing, and I made the best decisions I could in the circumstances in which I found myself.”

He continued, “I know in my heart of hearts that I have done no wrong and wronged no one.”

Despite opposition calls for an election, Mr. Ahern’s most likely successor is the deputy prime minister, Brian Cowen, who is also expected to assume the leadership of the Fianna Fail party.

Eamon Quinn reported from Dublin and Alan Cowell from London.

Eamon Quinn reported from Dublin, and Alan Cowell from London.