Florida on Tuesday became the latest and by far the largest US state to ban transgender women and girls from participating in school sports, part of a campaign in statehouses nationwide this year assailed as discriminatory by equal rights activists.

Republican governor Ron DeSantis, who is closely aligned with former President Donald Trump, enacted the law on the first day of Pride Month, which celebrates the lesbian, gay, bisexual, transgender, and queer (LGBTQ) community.

DeSantis signed the bill at an event at a Christian school in Jacksonville where he was flanked by several teenage women athletes. He said the law was needed to ensure fairness for women participating in sports across the state.

“I can tell you this: in Florida, girls are going to play girls’ sports and boys are going to play boys’ sports,” the governor said. “We are going to go based off biology, not based off ideology when we are doing sports.”

Supporters of the sports bills say transgender female athletes have an unfair advantage, having been designated male at birth but having since transitioned. Florida’s law defines an athlete’s sex as that stated on documents at birth.

The law, rushed through the state legislature as an attachment to a charter school bill, passed over the objection of Democrats and civil rights advocates who call the banning of transgender girls and women from sports unnecessary and discriminatory.