Israeli former foreign minister Tzipi Livni called on Saturday for three centre and centre-left parties to run a joint list against Prime Minister Benjamin Netanyahu in a January 22 general election.
Livni said her newly formed HaTnuah party had received positive responses from both Labour and the secular Yesh Atid party of former journalist Yair Lapid.
"I propose that the opposition form a bloc that can stop Netanyahu forming the next government," she told a campaign meeting in Tel Aviv.
"The three of us must unite under one roof and set all personal differences aside."
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Livni noted that the joint list of Netanyahu's rightwing Likud and the ultra-nationalist Yisrael Beitenu party was losing ground in the opinion polls and said it opened up the opportunity to woo voters who despaired of change.
The latest polls suggest Netanyahu's joint list will win between 34 and 36 of the 120 seats in parliament, down from the two parties' current 42.
Its ratings have been hit by a sharp rise in support for Jewish Home, a national religious pro-settler party projected to win 13 to 14 seats.
The polls predict between 16 and 18 seats for Labour, between nine and 10 for Livni's party and between nine and 11 for Yesh Atid if they ran separately.
Labour leader Shelly Yachimovich, another former journalist, said she welcomed Livni's proposal and that all three parties should follow her lead in publicly undertaking not to join any government led by Netanyahu.
Lapid said he was ready to meet the other two party leaders in the coming days but has so far refused to rule out joining a Netanyahu-led coalition.