Labor Party leader Shelly Yacimovich and Yesh Atid leader Yair Lapid joined forces Monday to attack Hatnuah chief Tzipi Livni, who last week launched a campaign to get the three center-left parties to unite.

"We were nothing but decoration on [Livni's] calculated spin that didn't have a smidgen of truth or content," the two said in a statement.

They released their statement in response to a video Livni posted online on Monday night in which she urged people to vote for a centrist party; Livni also posted a document on Facebook detailing what she says she proposed to Yacimovich and Lapid at a meeting on Sunday.

"I call on you today not to despair, not to throw up your hands. We - those who represent the center of the political map, the moderate majority that wants to live here - still want to fight for the face of the country," Livni said in the video.

"We ask one thing of you: Go out and vote. I'll obviously be happy if you vote for Hatnuah, which I head, but what's more important is that you go out and vote for one of the centrist parties. In this election, there are only two ballot slips: an extremist one and a moderate one. That of [Prime Minister Benjamin] Netanyahu and his natural allies, and ours, that of the centrist parties."

In the document, she said she proposed three things to Lapid and Yacimovich. They should work together until the election; promise to recommend someone from within the bloc as prime minister; and if Netanyahu gets the nod instead, decide jointly on whether to enter his coalition or remain in the opposition. In their statement, Lapid and Yacimovich called this "a false account of what happened" at Sunday's meeting.

"We came to the meeting out of the mutual respect each of us has for the other two, even though there are many ideological differences between us. We were stunned to discover that we were nothing but decoration on calculated spin that didn't have a smidgen of truth or content," they wrote.

Mental bloc

"It's now clear that the entire invitation to the three-way meeting was a maneuver by Livni, who is desperate about her deteriorating position in the polls, at the expense of the hopes of the voting public that wants change. This is the same Livni who prevented the establishment of a centrist bloc before [party] slates were submitted, and now she's continuing to mislead, divide and undermine the effort to create a worthy alternative to the extremist government."

Hatnuah was quick to return fire, saying the other two leaders' "violent response" proves they are coordinating their positions "to prevent the disturbing truth from coming to light: They are playing a game of personal interests instead of agreeing to the only plan that could give the public hope."

But both Livni and Lapid told Haaretz independently last night they wouldn't join a Netanyahu government without at least one of the other two centrist parties. Lapid said he would prefer to join the government and influence it from within, but wouldn't do so alone.