Furniture designers and boat builders are among the businesses that rely on rare timbers like Huon pine and blackwood, and which yesterday lobbied for a proposed law to be changed.

Fifth-generation furniture designer and manufacturer Craig Howard yesterday predicted his business would close if all the forests earmarked under the deal were protected.

He urged the Legislative Council to amend the legislation before State  Parliament, so protection of forests containing speciality timbers was delayed until more research was done.

``If we don't have the raw material on hand I will lose my job,'' Mr Howard said.

Boat builder Andrew Denman said creating more reserves would starve businesses like his of necessary material when demand for such products was rising.

``We're not saying don't reserve [those forests], but let's not reserve them straight away,'' Mr Denman said.

He predicted if that wasn't done then ``in 10 years we're stuffed - probably sooner''.

The pair made the appeal to the Legislative Council with Speciality Timbers Alliance members George Harris and Murray Jessup.

The inquiry is investigating whether or not the Tasmanian Forests Agreement Bill, which underpins a deal signed by signatories, is viable.

In other evidence provided yesterday:

 Former Labor forestry minister Julian Amos claimed Gunns executives had made threatening phone calls to an industry signatory at the start of the peace talks.

 Timber Communities Australia chief executive Jim Adams said the scope of a socio-economic study into the peace deal had been broadened, which would delay its completion.

 Mr Adams claimed signatories to the deal did not know what the final size of a World Heritage nomination would be until it was publicly announced by federal Environment Minister Tony Burke last month as 170,000 hectares.