The Labour MP for Mangere, Su'a William Sio, says it's a cultural affront that National's candidate in the seat appears to be using a Samoan title she's not entitled to.
A Matai title is a legally-recognised chiefly title bestowed as an honour by Samoan families and their villages.
The Samoan Ministry of Justice and Courts Administration has told Mr Sio it has no one registered under the name of Misa Fia Turner, the National candidate, and she is not entitled to use the title Misa.
"The Ministry also says that under Samoa's Lands and Titles Act 1981, 'the use of an unregistered Matai title is illegal as it is considered an offence to wrongfully use such a Matai title','' Mr Sio, a Samoan, says in a statement.
He says under Samoan law the 'rightful holder' is a person 'who has been appointed in accordance with the customs and usage of the Samoan people' which includes being recognised through a court judgement.
The rightful holder also has to have had a traditional appointment in the village to which that name or title belongs, he says.
"If National's candidate is using a title she has not had, that is an affront to the people of Samoa and the Samoan community in New Zealand."
Mr Sio says the National Party must investigate the discrepancy between Misa Fia Turner's title and the view of the Samoan Government.