A trafficking offence within 500 metres of a school would be punishable by a prison term of up to 25 years - an increase from 300 metres - under an amendment circulated by Coalition MP Robert Clark, the former attorney-general.

While the offences must occur in a public place, the increase in proposed distance from a school would ensnare dealers who operate near a notorious drug market in Richmond. Public housing towers south of Victoria Street are within 500 metres of Richmond West Primary School.

The amendment to 500 metres would bring Victorian laws in line with those in South Australia.

The laws apply to all illicit substances, not just ice, and include new offences as well as tougher maximum sentences for existing offences.

It is expected the laws will pass the lower house on Thursday, despite criticisms from both sides of politics and advocacy groups.

The Coalition says the laws do not go far enough, and the Greens and advocacy groups say they are the result of a populist overreach that will prove unworkable and could have unintended consequences.

Premier Daniel Andrews first proposed the laws while he was opposition leader during an appearance on Radio 3AW in August last year.

The Drugs Poisons and Controlled Substances Amendment Bill will be opposed by the Greens but supported by the Coalition, despite its misgivings.

Mr Clark said in Parliament on Wednesday that the laws would have minimal impact and reflected the government's failure to properly tackle ice, an approach that had "badly let down Victorians".

The Coalition would not oppose the bill, Mr Clark said, because it may make marginal improvements to ice laws.

But he used the debate on Wednesday to rail against the Sentencing Advisory Council and the Court of Appeal, and lament inadequate police numbers and the apparent capitulation of the Coalition's baseline sentencing regime.

"Now we face a real test of wills," he said. "Will we have the stronger sentences that the community needs and wants, or will we continue with weak and inadequate sentences?"

When the seven new offences were introduced into Parliament earlier this month, Mr Andrews said the laws were designed to take action against those peddling "an insidious drug".

"These laws will hold anyone who preys on children to full account and give police tougher powers to catch anyone who manufactures or sells ice and other illicit drugs," he said.

Mr Andrews said at the time that the issue was growing, with 28 offences detected by police at or near schools in 2014.

Victorian Alcohol and Drug Association chief executive Sam Biondo said the laws were more about style than substance, and could have the unintended consequence of forcing teenagers into the homes of drug dealers.

"There are other ways of dealing with this that would have far greater impacts," he said.

Colleen Hartland, a Greens Legislative Council member, said some of the laws risked criminalising teenagers unnecessarily.

"The government's so-called 'tough on crime bill' creates a range of new penalties which are either already covered by the law, so it is duplication and just purely for show, or they have increased already very high maximum penalties to extremely high maximum penalties, which the court is unlikely to take advantage of.

"I imagine the government believes these new laws are a cheap solution for the government to look like they are tackling ice, rather than making the required financial investment in treatment and rehabilitation, and in expanding the drug court approach across Victoria.

"They are a waste of the courts' time and limited resources and should be abandoned."