More medically supervised injecting rooms are needed across Melbourne, advocates say, as figures reveal overdose deaths remain at near-record highs.

In 2023, 547 Victorians fatally overdosed - three fewer than the state's deadliest year on record in 2022 - according to an annual report released on Thursday by the Coroners Court of Victoria.

About three quarters of overdose deaths occurred in metropolitan Melbourne, with a majority involving multiple drugs.

Diazepam, a sedative often used to treat anxiety, was the deadliest drug contributing to overdose deaths.

Heroin accounted for the second-highest number of overdose-related deaths, but overall numbers decreased from 230 in 2022 to 204.

Methamphetamines were the third-highest contributor.

The City of Yarra, which hosts a medically supervised injecting room in North Richmond, recorded 19 deaths - five more than the previous year.

The City of Melbourne, where the state government abandoned plans to build a second injecting room in the CBD, observed a fall in overdose deaths involving heroin - from 24 in 2022 to seven in 2023.

The Brimbank local government area in Melbourne's west recorded the second-highest heroin-related overdose deaths in 2023 with 14, a drop of five from 2022.

The Victorian Drugs and Alcohol Association said the data showed a clear need for more medically supervised injecting centres in high-risk areas across Melbourne, not just the CBD.

Chief executive Chris Christoforou said the growing adulteration of traditional illicit drugs with fentanyl and synthetic opioids "only increases the risk that fatal overdose numbers will grow".

Victorian State Coroner John Cain called for public health responses to be strengthened.

"Drug-related harms are complex and are driven by a variety of factors including changes in drug use, availability and regulation," he said.

"That is why coronial data is so integral to understanding how best to target resources and save lives."

The report found men were twice as likely to die from overdose, and people aged between 35 and 54 most at risk.

Premier Jacinta Allan in April ruled out a second injecting centre, instead investing $95 million in health measures including a new community service on Flinders Street and further outreach teams.

She reiterated on Thursday the government remained opposed to a CBD injecting facility.

"These are the measures that we are focused on rolling out statewide to continue to support people who need these life-saving treatments," Ms Allan told reporters.

Victorian festival-goers will be able to test drugs for potentially deadly chemicals as soon as this summer during an 18-month pill-testing trial.

NSW has been urged to adopt pill-testing after two people recently died and two others were hospitalised from heroin overdoses after using what they believed was cocaine at a house party in Sydney's inner west.

Overdose deaths will be discussed at a NSW drug summit, to be held in November and December and modelled on a 1999 event that was critical to the nation's first supervised injecting room.

Similar political courage is needed now, advocates say, amid dozens of overdoses nationally caused by synthetic opioids

Potent substances known as nitazenes are often sold as other drugs including cocaine, MDMA and heroin, with disastrous effects.