PROPOSED law reforms to make arsonists foot the bill for firefighting costs is unworkable, Australian Lawyers Alliance spokesman Greg Barns has said.
The new sentencing option is one of a suite of changes to Tasmania's arson laws being considered by cabinet, following recommendations made by the Sentencing Advisory Council last year.
Attorney-General Brian Wightman said the proposed change would send a strong message to the community that arson would not be tolerated.
But Mr Barns said prospective arsonists who were undeterred by the maximum 21-year jail sentence and existing ability for judges to make them pay for damage done were unlikely to baulk at this fresh penalty.
He said it was also unlikely a person convicted of arson, many of whom were youths or people suffering from mental illness, would be able to pay the cost of firefighting.
The firefighting and clean-up costs for the Dunalley bushfire - which was not deliberately lit - was more than $14 million.
"There aren't many multimillionaires who go around lighting fires deliberately," Mr Barns said.
About 40 per cent of the 4092 fires in Tasmania in 2012-13 were deliberately lit.
Tasmania Fire Service chief officer Mike Brown said that percentage was slightly lower for bushfires, most of which last summer were started by lightning strikes.
Mr Brown said he supported any proposed law changes that would make people think twice before lighting a fire.
The proposed laws are expected to consider other recommendations made by the advisory council, including separating arson for buildings, other structures and bushfires, and creating a new offence of arson causing death.
Mr Wightman acknowledged arsonists were unlikely to be able to pay back a multimillion-dollar bill, but said it was important to have as an option in circumstances where they could pay.
"I think it's very important that we send a strong message to the Tasmanian community that if people choose to light fires and they may cause significant damage, then they may have to pay for it," he said.
The legislation is expected to be before parliament next week or early November.