Stade Francais players have voted to go on strike in protest at a planned merger with bitter Paris rivals Racing 92, club vice-captain Pascal Pape confirmed to Agence France Presse on Tuesday.
Players were reported to have voted "99.8 percent" in favour of industrial action, and union chief Robins Tchale-Watchou told Reuters the Stade Francais team would start an "open-ended strike", meaning they would miss Saturday's trip to Castres.
The vote came a day after Racing's billionaire owner Jacky Lorenzetti and Stade Francais counterpart Thomas Savare announced proposals to create a super club from the two Top 14 outfits.
Pape described the move for Stade Francais as "the death of 136 years of the club's history" and players have raised fears of an unequal partnership in Racing's favour.
They called on their supporters to rally behind them at the club's Jean-Bouin stadium in Paris on Monday.
"It's hard to swallow," said Jonathan Danty, 24, the Stade Francais centre who is training with the French team for the Six Nations match against Wales in Paris on Saturday.
"We were always told we were the future of the club and that if we left, the club would be in danger. And now we find out they did this behind our backs," he said.
Rival clubs expressed fears over the creation of a new super club while the French Rugby Federation and the Paris government complained they had been kept in the dark about the move.