Former foreign minister Tzipi Livni has resigned from Israeli parliament, a month after she lost a battle for leadership of her Israel's main opposition party, Kadima.
In her resignation speech on Tuesday, she accused Israeli leaders of neglecting peace efforts with Palestinians.
"For years, Israeli leaders have been burying their heads in the sand, occupying themselves with political exercises and spin and in that time the threat to Israel has only grown," she said in televised remarks.
"There is an immediate and urgent need to reach a permanent settlement with the Arab world and the Palestinians."
She warned that Israel was sitting "on a volcano".
"The international clock is ticking and the existence of Israel as a Jewish and democratic state is in danger," she said.
Speculation about Livni's political future was rampant after she was defeated by Shaul Mofaz in party elections held March 28.
She said she would remain in public life, leaving open the option of running in the next election, which could be held as early as August this year.
Binyamin Netanyahu, th Israeli prime minister, signalled this week that he would soon call early elections.
The next vote is scheduled in October 2013, but an array of issues, including disagreements in Netanyahu's coalition over draft exemptions for ultra-religious Jews, threaten to tear the government apart.
A founder of the centrist Kadima Party, Livni served as foreign minister from 2006 to 2009, a time when she was Israel's chief negotiator with the Palestinians.
But in her three years as opposition leader, she faced heavy criticism for what was widely seen as an ineffective term.
Kadima, which won the most parliamentary seats in the 2009 elections but failed to form a government, looks set to do badly in the upcoming vote with opinion polls suggesting it could lose at least half its seats.