Workers at the Mini car plant have rejected a pay offer, raising the threat of the first strike at the factory since 1984.
Unite said its 2,000 members at the site near Oxford had voted by 97% against a deal which includes a 2.2% pay rise, because of "strings" attached.
The union said it was in dispute over a bonus payment and an agreement over extra hours and rest periods.
Talks are set to take place, but Unite said it will press ahead with preparations for an industrial action ballot.
National officer Roger Maddison said: "There are more strings to this deal than a puppet show and the workers at BMW will not accept it. The truth is that BMW has made a pay offer of just over 2%, and the rest of the deal comes with significant strings attached.
"The union never closed the door on talks and we are happy to get back around the table but we are also making preparations to ballot our members for strike action.
"The majority of the workforce work 11-hour shifts, and more and more productivity demands are being made by BMW. Rather than try to claw back every penny it can, BMW should be treating its workforce with dignity."
Rover owned the factory the last time there was industrial action, but German giant BMW now makes the Mini at the site.