Green Party co-leader Metiria Turei should pay back money she received on welfare as a solo mum after admitting she lied to authorities, a tax lobby group says.
Ms Turei said she didn't tell welfare officials she had income from flatmates when she was receiving a benefit while studying law in the 1990s.
"I knew that if I told the truth about how many people were living in the house my benefit would be cut," she said when releasing a families policy package on Sunday.
"And I knew that my baby and I could not get by on what was left.
"This is what being on the benefit did to me - it made me poor and it made me lie."
The New Zealand Taxpayers' Union says she needs to pay back the money she received from Work and Income as a result of her lying about her living situation.
"Putting aside the moral question of whether Ms Turei was justified in breaking the law back in the '90s, now that she can afford to pay it back, she must do so," the union's executive director, Jordan Williams, said.
Lying to Work and Income about subletting rooms is no different to a tax evader cheating on their taxes because they decide they need more money, he says.
"Now Ms Turei is an MP, earning around $200,000 per year, the very least she can do is pay back the money she's admitted to having defrauded."