Senator Milne told an anti- pulp mill meeting at Riverside last night that the report showed Gunns had made optimistic claims about the mill that carried inherent risks.

Senator Milne was one of three guest speakers who spoke to about 650 people.

The report - by actuary Naomi Edwards, who has previously queried Forestry Tasmania returns and spoken at an anti-mill rally to question the viability of the pulp mill - raised concerns over construction costs, fibre costs and foreign exchange impacts.

Senator Milne said Gunns hadn't considered the strengthening Australian dollar when discussing the mill.

"The foreign exchange impact would make this mill totally unreliable."

The report also pointed to a construction cost blowout to $2.5 billion from the original $1.4 billion, it said plantation fibre costs were higher than those modelled for a native- forest based feed stock and the mill would have a "lack of competitiveness" with South America.

A Gunns spokesman declined to comment on the report last night.

The report was launched at the Friends of the Tamar Valley community meeting at the Tailrace Centre last night.

Other guest speakers were psychologist Steve Biddulph and professor of politics Quentin Beresford.

Another anti-pulp-mill rally is scheduled for May 14 in Franklin Square, Hobart.

Senator Milne said the mill was a "disaster of a proposal" that was "totally unsuitable" for the Tamar Valley.

"All Gunns' economic assumptions assume that there is going to be no negative impact or risk to the environment or to people because of their pulp mill," she said

"But when you start taking the risk analysis into consideration you get a completely different outcome.

"It is a corrupt process that cannot be supported in a democracy and must not be supported with a single dollar of federal government funding."