Former prime minister Tony Abbott has torn into ACT Education Minister Yvette Berry for reminding schools of their obligation to be inclusive of lesbian, gay, bisexual, transgender and intersex students.

Ms Berry's caution came after Brindabella Christian College asked parents to vote no in the postal survey on same-sex marriage with a warning the school may no longer be able to teach Biblical views on marriage and family should the Marriage Act change.

Ms Berry said: "Of course school leaders, staff and parents and carers are free to hold their views on marriage equality but this cannot be allowed to occur in a way that damages the welfare of young LGBTIQ+ people."

Mr Abbott slammed Ms Berry's reminder as "a pretty outrageous interference with freedom of speech and freedom of religion".