Jessical Biel is an elitist "spreading disease to the 99 percent", according to a lawmaker behind an anti-vaccination Bill the Hollywood star opposes.
Biel is campaigning against a California state Bill which would crack down on parents fraudulently claiming their children can't be vaccinated for medial reasons.
She's denied being an anti-vaxxer, saying she believes in "giving doctors and the families they treat the ability to decide what's best for their patients".
But California Senator Richard Pan, a practicing pediatrician, says Biel is either "misinformed" or deliberately spreading misinformation.
"The only reason that [individuals like Biel] are able to do this is that they are counting on others to vaccinate their own kids for them," he told the Hollywood Reporter.
"How many people have to be hospitalised before people think 'this isn't right'? I wish the 1 percent would stop spreading disease to the 99 percent."
Biel said her friend's child is immuno-compromised, so is unable to get some vaccines.
A pro-immunisation campaigner told the Hollywood Reporter, which usually reports on film industry happenings, Biel and her friend should support the Bill - not oppose it - because the more people that are immunised, the less chance disease will have to spread.
"That child will be protected from exposure to a vaccine-preventable disease," said Leah Russin, executive director of Vaccinate California.
Bill co-sponsor Lorena Gonzalez of the California State Assembly said the Bill only excludes exemptions that medical science doesn't support.
The US is in the midst of its biggest measles outbreak since the 1990s. The World Health Organization earlier this year named the anti-vax movement as one of the top 10 threats to global health.
Biel is known for starring in movies The Texas Chainsaw Massacre and The A-Team. She married pop singer Justin Timberlake in 2012.