The prospect of Ireland electing Europe's first gay president is over after the leading candidate dropped out of the race following a scandal involving his former partner's rape of a 15-year-old boy.

David Norris announced he was withdrawing from the contest after it emerged he had written to the Israeli authorities in 1997 appealing for clemency for his former partner, Ezra Yitzhak Nawi. The Israeli peace activist was later found guilty of the statutory rape of the Palestinian boy and served time in prison.

On the steps of his Dublin home, Norris acknowledged the enormous damage inflicted on his campaign after appearing to be the popular choice with a consistent poll lead over his rivals.

While his decision to enter the race had made it possible for a gay candidate to stand for president, the independent senator said it was time to bow out.

"I would have loved to have had the opportunity as president of Ireland to extend that to the service of the entire people but that is no longer possible."

He said he had always conducted himself with the dignity and decorum that would be expected of any potential president. "The recent frenzy threatened to erode that principle and it is now time for me to reassert as far as possible control of my life and destiny."

Norris's fate was sealed on Tuesday night when members of the Irish parliament withdrew their support for his candidacy. Under the Irish constitution, a candidate cannot stand for the presidency unless he or she has the support of 20 TDs or senators, or command the backing of a number of county councils.

Norris had won the backing of one council while some councillors had refused to even meet him.

His campaign was also damaged by the resignation of several election workers over the Nawi scandal. They were angered over being kept in the dark about Norris's letters on Irish parliamentary notepaper to Israeli authorities, giving a character reference to his former partner and pleading for clemency.

Norris, Ireland's leading James Joyce scholar, refused to answer questions from the media outside his house on the street where he established the James Joyce Centre.

Defending his record, Norris said, speaking from a script: "I deeply regret the most recent of all the controversies concerning my former partner of 25 years ago, Ezra Nawi. The fallout from his disgraceful behaviour has now spread to me and is in danger of contaminating others close to me both in my political and personal life. It is essential that I act decisively now to halt this process."

With characteristic flourish, he added: "As I came across the Samuel Beckett bridge today into my mind came his words about humanity and frailty: 'Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.' "

Struggling to be heard among the media throng outside the house, a middle-aged woman cried out: "Stay in the race, don't let the media drive you out."

But Norris had already gone back inside, his attempt to succeed Mary McAleese as the head of the Irish state this October in ruins.