People in New South Wales caught manufacturing or supplying commercial quantities of the drug ice will now face the prospect of life behind bars.

The State Government announced that from tomorrow, the threshold required to charge people with dealing or making ice, will be lowered from 1 kilogram to 500 grams.

The maximum penalty available for the offence was also raised from 20 years' jail to life imprisonment.

NSW Attorney-General Gabrielle Upton said her Government was putting suppliers on notice.

"Drug manufacturers and dealers profit from misery and misfortune of others in our community," she said.

"The New South Wales Government believes that drug manufacturers and dealers of ice must be held to higher account."

Ms Upton said offenders could now be sentenced to life and fined $500,000.

"The ultimate aim is to cut off supply of these drugs, which we know are an epidemic across our state," she said.

"People are using ice more often and more people are using ice.

"It's having an impact on our communities in metropolitan areas throughout to regional New South Wales.

"So to help the users of these drugs, we need to take the supply of ice out of circulation and these tough new laws address dealers and manufacturers of drugs."

Punitive measures not based on evidence: drug expert

However, drug policy experts argue this change to the law is unlikely to address the problem.

"I think this is about being seen to be tough and the New South Wales drug threshold limits have a long history of being driven by public concern rather than by evidence," Professor Alison Ritter, the director of the Drug Policy Modelling Program at the National Drug and Alcohol Research Centre (NDARC), said.

Sam Biondo, the executive officer of the Victorian Alcohol and Drug Association, said many Australian jurisdictions were having ineffective kneejerk reactions to ice.

"On the surface it looks like the Government's doing something positive and is taking a strong stance," he said.

"[But] it actually creates greater incentives for others to come in and fill the gaps, it creates greater problems in terms of costs of prisons and enforcement with — for many of us looking at this problem — no greater benefit to the community."

Government did not consult over change: expert

Professor Ritter said she was concerned the NSW Government did not seem to consult with expert bodies before implementing the change.

"As far as I know, the Government hasn't consulted experts in relation to this, they haven't spoken with NDARC, they also haven't spoken with the Bureau of Crimes Statistics," she said.

"My view is that regulations and laws should be based on best available evidence, and that evidence needs to be brought into the debate about where you set these thresholds, and as far as I can see that hasn't occurred in this particular instance."

When questioned repeatedly by the ABC, the Ms Upton would not answer whether the NSW Government had sought expert opinion on the matter.

Mr Biondo argued governments should be focused on tackling the demand for ice instead of looking to change punitive measures.

He pointed to New Zealand as a model for fighting substance abuse.

"They've got a national drug action plan that's been segmented and operationalised according to a whole range of activities that need to occur," Mr Biondo said.

"They monitor it and evaluate it from year on year, and as I understand it, it started to have an impact on the use of methamphetamine in that country and it's actually reducing the demand and it's having positive effects in the community."