Letters from doctors excusing children from immunisation will no longer be accepted by Victorian child care centres and kindergartens, as the Government moves to toughen its "No Jab, No Play" laws.

The changes mean immunisation history statements from the Australian Immunisation Register will be the only documents accepted as evidence of a medical reason for a child not to be immunised.

Victorian Minister for Families and Children Jenny Mikakos said, under legislation being introduced to Parliament today, other medical documents would be rejected.

"In essence, this is in response to a very small group of dodgy doctors who are putting the community's health and safety at risk, who have been providing letters for parents with blanket exemptions, claiming that there is a medical reason for that child not to be immunised," she said.

"We're going to ensure there is only one set of documentation that will be accepted now."

Ms Mikakos said federal authorities were currently investigating doctors helping patients get around immunisation rules.

Victoria's No Jab, No Play legislation ban unvaccinated children from attending child care and kindergarten.

In August, Melbourne doctor John Piesse agreed to have his licence to practice suspended for issuing medical exemption certificates for children.

At the time he said what he was doing was "totally legal".

His practice in Mitcham was raided in September by the Australian Health Practitioner Regulation Agency (AHPRA) and police officers.

Federal Government records from 2015 showed about 30,000 Australian children — about 1.34 per cent — were granted "conscientious objection" exemptions from vaccination

Vaccination science is 'crystal clear'

Ms Mikakos also said the changes would make the process much easier for early childhood learning services, who will now only have to deal with one set of documents for each child.

"Parents will also need to provide these immunisation history statements at regular intervals to make sure kids are up to date," she said.

Opposition Leader Matthew Guy said he supported any changes to boost important vaccinations.

Ms Mikakos said overall rates of immunisation had increased in the two years since the No Jab, No Play laws were introduced.

"I'm pleased to say Victoria has now hit 95 per cent of five-year-old children being immunised, which is a very positive outcome," she said.

"We know the science is crystal clear — vaccinations are safe and they are saving lives."