The stage is set for a labour conflict at Rio Tinto Alcan's Alma, Que., operations as workers there have rejected what the company describes as a final offer.
Workers from three negotiating units voted down the proposed deal by margins of 71 per cent, 88 per cent and 98 per cent.
They were following the advice of their union's executive committees, all of which recommended that members refuse the offer.
The sides in the dispute haven't been able to agree on conditions related to subcontracted labour.
The Alma facility hosts one of Rio Tinto's largest Quebec aluminum smelters.