The "special reasons" exception – which has been used by criminals to avoid jail after attacking police, paramedics or prison or youth justice officers – will be narrowed even further so that drugs and alcohol can no longer be used as an excuse.

Sentencing Advisory Council chair Arie Freiberg warned on Tuesday that removing exemptions from mandatory sentencing on people who attack and injure emergency services workers would not make the community safer.

“I think it’s a measure designed to assuage public concern but might be ineffective, unfair and unproductive,” he said.

The Law Institute of Victoria also expressed alarm at the government’s move to toughen laws, which will mean the mentally impaired will be even more likely to face jail time.

Mr Freiberg said the public would be less inclined to want harsh sentences when told of the full circumstances in an offender’s case.

The government will also introduce legislative changes to treat serious attacks on emergency services workers as a category one offence, alongside rape and murder.

Premier Daniel Andrews said the government would hold discussions with emergency services unions about how the new law will treat "narrow and specific" cases where mental impairment may have contributed directly to someone's conduct. He said the new laws would still allow defendants to plead not guilty due to mental impairment.

The Law Institute of Victoria will seek an “urgent meeting” with Attorney-General Martin Pakula to discuss its concerns.

The institute’s president, Belinda Wilson, said every assault case was different and it was crucial judges and magistrates retained discretion.

“There are often serious mental health issues involved in these vicious assaults on emergency workers,” she said. “These mental health issues must be taken into account.”

The legislative changes will apply to anyone guilty of an attack on police, paramedics, firefighters, or emergency department nurses and doctors.

The latest available figures dating back to 2013 show mental health accounted for as much as 20 per cent of Ambulance Victoria’s workload.

The state government has been scrambling to react to the case of two women who were jailed for a serious assault on two paramedics but then released on appeal.

Amanda Warren, 33, and Caris Underwood, 20, attacked two paramedics in Reservoir after a day-long binge on bourbon, champagne and cannabis in March 2016.

They were last year jailed by a magistrate for eight months and four months, respectively.

But last week County Court Judge Barbara Cotterell decided to quash their jail sentences, saying the pair had made "enormous" efforts to turn their lives around after "appalling" childhoods and battles with drug, alcohol and mental-health problems.

Details contained in Judge Cotterell's full reasons, which outline Warren’s and Underwood’s childhoods, cannot be published for legal reasons.

However, the judgement reveals Warren spent time in psychiatric residence, where she met her current partner, who has been diagnosed with schizophrenia.

County Court Chief Judge Peter Kidd told ABC Melbourne that mandatory sentencing meant mercy could not be dispensed even if a particular case warranted it.

Judge Kidd also criticised sections of the media for their "denigrating" coverage of Judge Cotterell's decision.

"Sometimes the media coverage can be pretty vicious and that can have an impact on judges," Judge Kidd said.

But Opposition Leader Matthew Guy said he was worried the changes, which include a direction that judges should give "less weight" to an offender's circumstances, would leave too much discretion with the courts.

"We're concerned that this is in fact no change at all," Mr Guy said on Tuesday morning.