A rule which stops mothers from giving their newborn baby a hyphenated surname in the Cook Islands is being called discriminatory and disempowering to women.
Ministry of Justice policy only allowed newborns to have their mother's last name if the father was unknown.
Democratic Party leader Tina Browne said the rights of the mother must be recognised.
"This policy clearly discriminates against the undisputed right of a woman to give her surname to her child and if she wishes her child to have a hyphenated surname," she said.
There was no legal or moral basis for enforcing this policy and it went against the Cook Islands' Constitution, the opposition party leader said.
"We boast about having gender equality, that women are treated equally to men in our society and here we have a government ministry that is perpetuating uncompromising, well out-of-date attitudes and rules that do nothing to recognise the rights of women."
All birth registration forms and marriage applications - which refer to the bride as being a "spinster" - urgently needed to be brought up to date, she said.
"We urge the minister of Justice Rose Toki Brown to take the lead on this and direct her ministry to make the necessary changes in recognition of the fact that it is the 21st century and attitudes have changed a lot since the 1970's - empower our women and give them the recognition they must have," she said.
Parents are told their only option was to register with the father's name and then change it by deed poll to a hyphenated name - a process Browne said was making things unnecessarily complicated and difficult for young couples.
Lawyer Heinz Matysik, who is acting on behalf of a couple wanting to register their baby girl, said there was no explicit provision in the Births and Deaths Registration Act 1973 which required the registration of the father's surname.
"The Ministry's insistence that the father's surname is to be taken, without any reference to the wishes of the mother, or both parents for that matter, is undeniably discriminatory and out of step with societal norms and expectations in 2021," Matysik said.