Tommy Lapid has resigned as leader of Israel's Shinui Party, a day before members were poised to oust him.
Tommy Lapid is a former Israeli deputy prime minister
Mr Lapid said Shinui, a centre-right secular grouping, "in its present form is not worthy of the public's trust".
The party has been damaged by a recent split over who would be deputy leader.
Recent polls suggest Shinui, which has 15 Knesset seats, would struggle to win a single seat in elections in March, following the emergence of the Kadima party founded by Ariel Sharon.
"I have decided, with genuine sadness, to resign from my post as chairman of Shinui, as the head of the Shinui list, and as a member of the Shinui party," Mr Lapid told reporters.
"A chapter of my life has been completed, a chapter of which I am proud. Thank you."
A Yugoslavia-born Holocaust survivor, the 73-year-old Mr Lapid emigrated to Israel in 1948.
Before becoming an MP in 1985, he spent five years as the director-general of the Israeli Broadcasting Authority.
In 1999 Mr Lapid was elected leader of the Shinui, and he launched a fiery campaign against Israel's powerful religious parties.
Running under the slogan "For a secular, free and democratic Israel", Shinui performed unexpectedly well in the January 2003 general election.
The party joined Israeli Prime Minister Ariel Sharon's coalition government and Mr Lapid was appointed both deputy prime minister and justice minister.
He served in the posts until December 2004, when Mr Sharon sacked Shinui after its ministers voted against his annual budget in a dispute over subsidies given to religious parties.
Earlier this month, a group of party backbenchers divided the party after they sidelined Mr Lapid's deputy, Avraham Poraz.
"If I received substantial credit for Shinui's accomplishments, I must take responsibility for the current crash of the party. I take responsibility, but I don't feel guilty," Mr Lapid said.