Israel’s embattled opposition leader has turned down an offer to join Benjamin Netanyahu’s Likud-led government, after ultra-nationalist coalition partners threatened to leave.

Asked this week about Netanyahu’s offer, Isaac Herzog told Army Radio: “That option has been exhausted,” before blasting the prime minister for “promoting fear and hysteria” and for “shooting his mouth off”.

Herzog’s snub could be aimed at shoring up his own support, amid an internal Labor Party war, in which he is fighting to stay leader, after talks to join Netanyahu’s coalition earlier this year enraged left-wing colleagues.

Herzog leads the main opposition party, Zionist Union, which is itself an amalgamation of his Labor party and Tzipi Livni’s party Hatnua. The combined group commands 24 of the Knesset’s 120 seats.

Despite his rejection of power-sharing, Herzog’s predecessor Shelley Yachimovich continued her criticism of the party leader this week, despite him surviving a no-confidence vote on Sunday.

Herzog’s rejection puts pressure on Netanyahu to accommodate former settler leader Naftali Bennett, whose religious nationalist Jewish Home party pushes for settlement expansion on tougher measures against Palestinians.

Herzog’s refusal will offer feel like revenge – Netanyahu recently spent weeks negotiating a deal with him, only to turn at the last minute to former foreign minister Avigdor Lieberman and his six-seat Yisrael Beitenu instead.