Pope Francis launched a fresh critique Friday of gender ideology, saying it was "the worst danger" which "erases differences".

"It is very important that there is this meeting, this meeting between men and women, because today the worst danger is gender ideology," the 87-year-old told a meeting with participants of an international conference on marriage and faith.

"I asked for studies into this ugly ideology of our time, which erases differences and makes everything the same. Erasing differences is erasing humanity."

The Argentine pontiff has repeatedly railed against gender theory, also called gender ideology, which broadly speaking is the idea that you do not have to adhere to the gender you were born with, and that gender is a product of societal norms, rather than purely biology.

In 2019, the Vatican published an educational document intended to help Catholic school teachers counter ideas which "deny the natural difference between a man and a woman".