AFP - Israel's centrist Kadima party headed by former foreign minister Tzipi Livni on Monday rejected Prime Minister Benjamin Netanyahu's offer to join a broad-based coalition.

"The prime minister's proposal as relayed to the Kadima chairman does not express an honest desire for such partnership," MP Yohanan Plasner told reporters after Kadima's parliamentary faction unanimously rejected the offer.

"A unity government has many advantages, but a national unity should not be an empty expression, but a commitment for a real partnership with a joint vision and principles and an agreed way to materialise these principles."

Netanyahu met Livni twice in recent days after inviting her to join his government and form a coalition "to face the national and international challenges facing Israel today."

Kadima, the largest in the 120-member parliament with 28 MPs, has been rocked in recent days by earlier reports the premier pressed several of its MPs to break away and join his coalition.

Livni accused Netanyahu of applying "gutter politics," saying he had made his offer after "he failed to split Kadima despite his efforts to do so."

Netanyahu's offer "cynically uses threats. We are not in war or in a peace process," Livni told reporters after the party vote in parliament.

The premier's office said in a statement he was "sorry to hear about Kadima's rejection... In view of the challenges facing Israel, the prime minister hoped for a different position."