A Canberra Liberal MLA has labelled a law making it easier for transgender teenagers to change their sex on government documents "unbelievable" and "completely out of touch".
This is despite his party never opposing the laws on the floor of the Legislative Assembly when they passed on Thursday.
Member of Brindabella Andrew Wall emailed constituents saying the government had passed the laws "behind the backs of parents".
Under the new laws, young people who are 16 will be able to apply directly to the registrar to change their details.
Young people over 12 but under 16 will be able to apply to the ACT Civil and Administrative Tribunal for leave to apply to the registrar.
It does not affect existing requirements for consent to hormone treatment or other medical treatments for gender dysphoria.
The Liberals did not oppose the bill in the chamber, or call for a division during voting.
However, they put forward amendments which would have increased the age at which a young person could apply to ACAT for leave to change their birth certificate without their parents' permission from 12 to 14.
Mr Wall said the government was dividing families.
"When we need governments and policy-makers focused on jobs and the economy, they are focused on ideology," he said in the email.
He claimed it would be a permanent decision and compared it to a child under 18 being able to get a tattoo without parental consent.
"From now on, your 12-year-old son or daughter can apply to erase their birth sex on their birth certificate and replace it with whatever gender they decide," Mr Wall said.
"Without your knowledge or consent. I think that's a pretty big deal, too. It's one of those decisions that should absolutely involve parents."
Mr Wall declined to comment about his email when contacted by The Canberra Times.
But Opposition Leader Alistair Coe said the party supported the principle that every individual should live their life to their fullest capacity.
"We are compassionate to those facing these challenges," he said.
"There are many competing factors and no easy answers. We commend families who face challenges together, which is why we all support allowing people younger than 16 to make changes with the care and guidance of their parents."
Chief Minister Andrew Barr said Mr Wall must explain why he did not oppose the legislation on the floor of Parliament on Thursday, if he was so opposed to the laws.
"The dog-whistling that we have seen from Liberal candidates and MLAs in the last week on issues like gender diversity, inclusiveness and LGBTIQ+ matters speaks to their true values," he said.
"No matter how hard Mr Coe tries to hide the fact that he and his party aren't hardcore conservatives, we get example after example of their ultra-conservative values.
"It is what they say behind closed doors, when they think people won't see or hear it, that displays their true values."