A Bill to stop convicted child sex offenders from changing their name has passed the first hurdle.

MORE: Government urged to rethink child sex offender register

National MP Jian Yang's private member's Bill was voted through the first reading last night. He believes it's important to make sure sex offenders can't just adopt a new identity.

"It will also reassure parents that they can have faith in the vetting of anyone being employed in a job related to children."

But the move is being dismissed as meaningless by Labour's children spokeswoman Jacinda Ardern, who said all the Bill does is give a false sense of security.

"A person can lawfully use a name without registering it, so long as the new name is not used for fraudulent or improper purposes. The new identity is established simply by using the new name and by repute."