An amendment to the existing law, which requires a minimum six months behind bars for anyone who attacks an officer on duty, will be introduced to state parliament on Tuesday to close an existing loophole.

It comes after James Haberfield, 22, avoided a prison term last year after admitting to attacking a paramedic at musical festival while on a cocktail of drugs.

Instead, Haberfield was ordered to serve 18-month community corrections order and undergo treatment for schizophrenia, which he suffered at the time of the attack.

The sentence sparked outrage among the community, his victim and the paramedic and police unions.

Attorney-General Jill Hennessy said the new legislation will allow people who assault emergency workers to claim "special reasons" in court for a "very narrow set of mental impairments".

Under the change, if a person's mental state is self-induced from alcohol or drug use they will not be able to rely on the "special reasons" clause.

"We are making the test much harder for people to demonstrate that they were suffering from the impacts of mental impairment," Ms Hennessy told reporters.

"We will be making it crystal clear that there needs to be very strong and compelling evidence that a person was not suffering from the applications of self-induced intoxication. "

The Office of Public Prosecutions will also now prosecute cases, rather than police, in higher courts.

The step comes as the state government reached an in-principle agreement with the Victorian Ambulance Union over paramedic pay and conditions, bringing an end to enterprise bargain agreement negotiations.

The agreement is in line with government wages policy, which caps annual pay rises at two per cent but includes a number of improvements to conditions.

They include making it easier for paramedics in the army reserve to take leave to fulfil their duties and providing greater flexibility for paramedics to address needs in rural and regional communities.

Australian Associated Press