The head of Israel's opposition Labor Party, Amram Mitzna, resigned Sunday, three months after leading his faction to its worst-ever electoral defeat.
Mr. Mitzna, a former army general and strong advocate of peace-making with the Palestinians, announced his decision at a hastily convened news conference.
He said he was handing back his "mandate" and resigning as head of the Labor Party.
His announcement came three months after he and his faction suffered a humiliating electoral loss to Israeli Prime Minister Ariel Sharon's Likud faction, which easily won a second term in office.
Mr. Mitzna blamed senior members of the Labor faction for driving him out of the leadership position. He accused some figures in Labor of incessantly working to undermine him since the January 28 national elections.
He said members of Labor were more interested in fighting against his leadership than in "fighting for peace."
While Mr. Mitzna did not mention names, it was widely reported in the Israeli media that he was mainly referring to the former defense minister, Binyamin Ben-Eliezer.
The two have clashed repeatedly since the elections, and Mr. Ben-Eliezer has reportedly used his influence within Labor to block proposals by Mr. Mitzna.
A former mayor of the northern Israeli coastal city of Haifa, Mr. Mitzna was elected head of Labor less than six months ago, ousting Mr. Ben-Eliezer.
Among those expected to contest the leadership following Mr. Mitzna's announcement are Mr. Ben-Eliezer and Matan Vilnai, a former military commander.
Mr. Mitzna campaigned in the January national elections on a platform pledging to re-start negotiations with the Palestinians, without pre-conditions.
His message failed to appeal to most Israelis, who have shifted increasingly to the right since the start of a violent Palestinian uprising nearly three years ago.