It has been revealed signatories to Tasmania's forest peace deal were kept in the dark about the final size of a Wilderness World Heritage Area nomination.
The key industry and environmental groups wanted an extra 124,000 hectares added as part of an agreement to end the state's forest wars.
But Federal Environment Minister Tony Burke last week submitted a nomination to increase the heritage area by 170,000 hectares.
Jim Adams from Timber Communities Australia has told an Upper House inquiry the figure was a surprise.
"Right up until the day that was done we believed it was 124,000," he said.
"We weren't aware the nomination had been increased beyond that.
"It's our understanding that increase in the nomination takes in a range of other areas which were otherwise already in reserves of one form or another."
Nelson MLC Jim Wilkinson has expressed frustration with the change.
"It seems to be a bit of a moving feast," he said.
"You entered into this, first there was the agreement that was entered into; then after the agreement there were the negotiations that have changed that.
"Now, of course, this seems to be yet another change. Yet the Legislative Council has been told 'look, if you make any changes at all the deal's off'."
A long-awaited socio-economic study into Tasmania's forest peace deal has been delayed.
The Commonwealth-commissioned study was supposed to be completed last month.
But the inquiry has been told the project's scope has been widened.
Mr Adams a says it is now also examining the impacts of having no deal.
"Initially it was set up to assess the impacts of the proposal."
"What they now are also trying to do is say 'well ok, what would the impact be of doing nothing?'
"That means they've now had to go back and do some additional work in terms of how, you've got to make some assumptions about that," Mr Adams said.