The future of the Tiwai Point smelter is being questioned as falling global aluminium prices and the high New Zealand dollar eat into profits.
New Zealand Aluminium Smelters says 100 jobs will be cut in the coming few years and renegotiating the company's electricity deal with Meridian Energy is now crucial.
Peneral manager Ryan Cavanagh says the cost of the electricity will go up in January and that will put more strain on an already deteriorating situation.
The smelter made a loss of $20 million last year.
Meridian Energy won't guarantee a new deal, saying it has an obligation to its own shareholders.
But Venture Southland says Meridian may have no option, because the Manapouri power station will be left stranded if the smelter closes.