A plan for Victorian paramedics to take the lead on emergency mental health call-outs has been put on hold over fears it would increase pressure on ambulance services.

The final report of a royal commission into Victoria's mental health system in 2021 recommended mental health-related triple zero calls be diverted to Ambulance Victoria rather than Victoria Police.

The health-led response was set to roll out on September 1 but has been pushed back indefinitely under changes to the Mental Health and Wellbeing Amendment Act introduced to state parliament on Wednesday.

"Now is not the time for us to pretend that ambulance services are where we want them to be and then embark on a really significant reform," Premier Daniel Andrews told reporters.

"I'm not here to make any apology for focusing on getting ambulance response times back to where we want them to be.

"That needs to be our priority."

Mr Andrews said it was a question of when, not if, the reform would take effect and the Victorian government would monitor factors including winter demand, staff illness and recruitment, and the impact of the federal boost to Medicare.

Victoria's latest ambulance performance data from January to March showed the system was continuing to buckle under pressure.

Paramedics were called to 92,413 code one cases - the most time-critical emergencies - in the quarter and responded to 65.2 per cent within the benchmark of 15 minutes.

Despite a marginal improvement on the previous quarter, it remained significantly lower than the 2014 response rate of 73 per cent.

Police will still be called to a small number of acute mental health cases to promote paramedic safety as part of ongoing dual responses once the change is implemented.

Ambulance Victoria already responds to more than 60,000 mental health-related cases a year, with police aiding paramedics with 25,000 of them.

In a statement, an Ambulance Victoria spokeswoman said significant work was under way to safely transition to the health-led response.

A Victoria Police spokeswoman said that work involved the force, government, health department and other agencies.

"Victoria Police's existing response to mental health call-outs remains in place," she said.

Opposition mental health spokeswoman Emma Kealy accused Labor of botching the royal commission reforms after it highlighted police visits could be humiliating and traumatic.

"Labor was warned to bolster the mental workforce back in 2019 and has failed to do so," Ms Kealy said in a statement.

Despite acknowledging the impost of the change to mental health call-outs, the premier was comfortable paramedics would be able to shoulder any extra load created by the decriminalisation of public drunkenness in November.