She explained her change of heart by saying it stemmed from "an ideological awakening."
"A party is not a value," she added. "It's a tool for the implementation of a point of view. The best thing one can offer its voters is being faithful to one promised them. As Knesset member I make a point of doing that."
Yacimovich also used the chance to slam Labor Chairman and Defense Minister Ehud Barak.
"There is no doubt that the Labor party is conducting itself in a bad way. I have heavy criticism of Barak. First, the willingness to be part of any government not thinking one step ahead.
"Second, the willingness to take part in a policy that is utterly foreign to our values, and thirdly his responsibility for a grave damage of partisan democracy."
She later criticized Barak's personal conduct, namely his residence in an upscale northern Tel Aviv building complex.
"He will not leave the coalition under any circumstance – since it is right for him on a personal level. His lifestyle is lavish and excessive and it's very hard for the public to accept a man who is supposed to represent it who lives such a lavish, ostentatious lifestyle," she said.