On Wednesday Gunns announced that its proposed $2.5billion pulp mill would operate totally on plantation timber, sparking calls from The Wilderness Society to renegotiate the wood supply deal to exclude native forest woodchips.

The Wilderness Society says the wood supply deal locks in more than one million tonnes of native forest wood for the next 20 years.

Gunns spokesman Matt Horan said yesterday that operations outside of the pulp mill were reliant on the wood supply deal and that it would not be renegotiated.

Mr Horan would not comment on the cost implications of the decision to make the pulp mill feedstock 100 per cent plantation wood.

"We will not make any further comment on the announcement," he said.

Forestry Tasmania managing director Bob Gordon said that Gunns' announcement was not unexpected.

"It is a matter of fact that pulp mills prefer young plantation wood and it was always intended that the Gunns mill would be plantation-based," he said.

Mr Gordon said that the wood supply deal covered a range of products including saw and veneer log, biomass and pulpwood, including a significant component from Forestry Tasmania's own plantations.

The Wilderness Society pulp mill campaigner Paul Oosting called on Premier David Bartlett to put pressure on the two companies to draw up a new agreement.

"Until Tasmanians see Gunns' native forest wood supply deals renegotiated and ancient forests properly protected, Tasmania's forests will continue to be logged, burnt and exported overseas and they won't have confidence that native forests will never be used in the mill," said Mr Oosting.

But Mr Bartlett said that it was out of his hands.

"It's a commercial arrangement between Forestry Tasmania and Gunns," he said, refusing to answer any more questions on the issue.