Hundreds of members of the Young Labor movement have moved to the Kadima party in recent weeks, including the former head of the movement, Maayan Amodai.
On Wednesday Amodai said that over the past two days hundreds of Labor activists have submitted membership requests to the Kadima offices.
Kadima, which heads the opposition, confirmed the report.
Labor Party members said in response that the new recruits would assist Knesset members Amir Peretz and Eitan Cabel secure a spot on Kadima's roster for the next elections.
Peretz and Cabel claimed they have nothing to do with the activists' move to Kadima, but sources within the political establishment said the two have been working to increase their chances in the Kadima primary elections.
The two lawmakers are permitted to quit Labor only as part of a group consisting of one third of the faction's members.