Labor officials are concerned that the merger with Orly Levi-Abekasis' Gesher party and the decision not to unite the center-left bloc will cause voters to cease supporting the party.
Some Labor supporters have already canceled their party membership, Israel Hayom reported, and others are deciding whether to follow suit.
Labor Chairman MK Amir Peretz clarified Sunday that the party management "unanimously approved the agreement to run together with the Gesher party." He also said that "there is no chance that Labor will join with [former Prime Minister Ehud] Barak or Meretz."
Israel Hayom noted that Labor's MK Stav Shaffir, however, is interested in merging together with Barak's new party, "Democratic Israel," as well as with Meretz.
Meretz, meanwhile told Israel Hayom that "all options are being considered, including Democratic Israel."
For its part, Democratic Israel would be open to joining with Shaffir, if she decided to leave her party.