The comedian has posted a series of angry messages to his 14 million followers accusing the Californian government of being a "corporate fascist".

In the outburst, the 53-year-old father says the government is "poisoning more children" by enforcing vaccinations.

The Ace Ventura: Pet Detective actor's comments come after a new bill removed parents' right to opt out of vaccines for their children.

Now parents can send unvaccinated kids to school only if they have a doctor's note.

The law comes after a recent outbreak of measles that started at Disneyland and was blamed on unvaccinated children.

After Twitter followers debated with Carrey, he sent another series of messages trying to justify his opposition, saying he was not anti-vax, but anti-neurotoxins.

Experts have been quick to disagree.

"Yes, Mr. Carrey, you are anti-vax," science writer Phil Plait says, accusing Carrey of cherry-picking information to make his case. "You can't pick and choose what to believe in and what not to, and then say you're not anti-vaccine."

Professor Arthur Caplan, of New York University's School of Public Health, agrees, accusing Carrey of spreading misinformation.

"The childhood vaccine schedule has been proven safe, and arguments about 'dangerous' ingredients have been proven incorrect over and over," he writes.

"Not only is Carrey ignorant when it comes to vaccines, he is a fool when it comes to using terms like fascism," Caplan continues.

"Fascism is when a government imposes its will upon the people by fiat. Nothing like that has happened in California – not even close. The legislature heard testimony, debated and then voted through the law to end liberal exemptions. Passing a law through the legislature and having the governor sign it is called democracy!"

Fairfax Media