Florida Governor Ron DeSantis on Tuesday signed a law prohibiting transgender women and girls from competing in girls and women's sports at public schools in his southern US state.

"We believe that is very important that the integrity of these competitions are preserved," said the Republican governor as he signed the measure into law at a Christian school in the northeastern city of Jacksonville.

"In Florida, girls are going to play girls' sports, and boys are going to play boys' sports," he said. "We're gonna go based on biology, not based on ideology when we're doing sports."

The law, which goes into effect on July 1, requires girls and young women to state their biological sex through their birth certificate in order to compete in a team.

DeSantis signed the measure on the first day of LGBTQ Pride Month.

Florida Governor Ron DeSantis, a staunch Republican, signed a law banning transgender women and girls from competing in girls and women's sports at public schools
Florida Governor Ron DeSantis signed a new bill that will fine businesses and hospitals that require COVID-19 vaccination from employees. AFP / MANDEL NGAN

"Appalling," tweeted Florida state representative Carlos Smith, a Democrat who identifies as Latino and gay.

"First day of LGBTQ Pride Month and @GovRonDeSantis signs SB 1028 which bans trans kids from school sports... This fuels transphobia and puts vulnerable kids at risk for no good reason," he wrote.

The Human Rights Campaign, a group defending the rights of the LGBTQ community, announced said it would challenge the measure in court.

"Gov. DeSantis and Florida lawmakers are legislating based on a false, discriminatory premise that puts the safety and well-being of transgender children on the line," wrote Campaign president Alphonso David.

"Transgender kids are kids; transgender girls are girls. Like all children, they deserve the opportunity to play sports with their friends and be a part of a team," David said.

Florida now becomes the most populous US state banning transgender women from female sports, joining other states with Republican governors that have recently approved similar measures.