The US Supreme Court has ruled that anti-discrimination laws apply to gay and transgender individuals, in a major win for rights activists.

Monday’s 6-3 ruling means the law barring workplace discrimination on the basis of sex also applies to sexual orientation, meaning workers can sue if they are fired over their orientation.

The three dissenting votes were all from conservative judges.

The majority opinion was delivered by Justice Neil Gorsuch, who was appointed by US President Donald Trump.

Three cases were filed by individuals who had all been fired for revealing their homosexual or transgender identities.

Only one of the individuals, Gerald Bostock, is still alive.

Legal aid group the American Civil Liberties Union represented two of the cases.

“There is no question: LGBTQ people are protected from discrimination in the workplace,” the union said in a tweet, using an acronym for gay, lesbian, bisexual, transgender and queer people.

Bostock was fired from his long-held job in the state of Georgia as a child welfare services co-ordinator after he joined a gay sports club.