United Nations ? The U.N.’s top refugee advocate resigned Sunday amid a festering controversy over allegations that he sexually harassed several female employees at the U.N. refugee agency.

Ruud Lubbers, the U.N.’s High Commissioner for Refugees, proclaimed his innocence in a letter of resignation, saying an internal U.N. investigation into his conduct failed to “prove that sexual harassment has taken place.”

Sunday’s resignation marked the end of a long career for Lubbers, who served as the Netherlands’ longest governing prime minister from 1982 to 1994. Lubbers, 65, lashed out at Secretary General Kofi Annan, who had cleared the Dutch official of wrongdoing, saying he had bowed to media pressure to force him out.

“For more than four years I gave all my energy to UNHCR,” said Lubbers, who has led the agency’s 6,000 staff members since January 2000. “To be frank, despite all my loyalty, insult has now been added to injury and therefore I resign as high commissioner.”

Lubbers’ announcement followed a meeting Friday during which Annan said he would pursue legal action to force the refugee chief from his job if he didn’t resign. At the time, Lubbers denied he’d been asked to resign and vowed to remain until his term ends Dec. 31.

It remains unclear when Lubbers will step down. He said he would continue to be “available for the cause” until a successor has been confirmed by the General Assembly. That process could take months.