Further doubt has been cast over the future of an aluminium smelter in Tasmania's north-east after a federal MP said it would not be eligible for a green energy scheme.

Further doubt has been cast over the future of an aluminium smelter in Tasmania's north-east after a federal MP said it would not be eligible for a green energy scheme.

A major aluminium smelter, which has a quickly approaching deadline to lock-in a long-term electricity deal, won't be able to rely on green credit help.