Labour list MP Moana Mackey is using taxpayer money to rent her Gisborne electorate office from her mother.
Politicians must declare any pecuniary interests but the arrangement is within the rules for MPs, who are given a capped allowance to cover the cost of running offices outside Wellington.
Ms Mackey, recently promoted by Labour leader David Cunliffe, has an office in Customhouse St in Gisborne which property records show belongs to her mother Janet Mackey.
The pair were the first mother and daughter pair together in Parliament when Moana Mackey was elected through the Labour list in 2003 and Janet Mackey was the Labour MP for the East Coast electorate, until retiring in 2005.
Janet Mackey purchased the heritage building in April 2009 for $200,000 where Ms Mackey and the late Parekura Horomia, the Labour MP for Ikaroa-Rawhiti, shared their offices.