Labour MP Chris Hipkins has been blasted for a lack of judgment over a question about New Zealand citizenship linked to questions about Australia's Deputy Prime Minister Barnaby Joyce's eligibility to be in Parliament.

Hipkins claims he didn't know the question, first put to him by a friend in the Australian Labor Party several weeks ago, was related to queries around Joyce's citizenship.

Had he known he says he might have given it a second thought, but Labour leader Jacinda Ardern says he shouldn't have got involved regardless.

Joyce's position in Australia's federal parliament will be examined by a court later this month after it was revealed he has New Zealand citizenship by descent through his father.


It was Hipkins' inquiry and questions from Australian media that led to the New Zealand officials notifying Joyce of his status.

Ardern on Tuesday admitted Hipkins lacked judgment in asking the question and told him as much.

"Regardless of what information was known this was not an appropriate question for us to be asking or to be involved in," she said.

Hipkins said he didn't know when he asked it where the question was going to end up, and had learned his lesson.

"I should have given it more thought... probably the lesson for me in this is where it potentially might involve the politics of another country, a little bit more homework and background checking before getting involved would be a useful thing to do."

Hipkins said he asked the question out of his interest in the rights of Kiwis living in Australia.

Prime Minister Bill English also leapt in to criticise Hipkins' judgment, saying he couldn't remember a time an MP involved themselves in another country's politics.

"It's another mis-judgment in the Labour Party about an issue that's quite serious and Mr Hipkins should have known that - there's been a lot of Australian publicity about what's happened to MPs."


Senators Scott Ludlam, Larissa Waters, Matthew Canavan and Malcolm Roberts have all faced questions about their citizenship within the last month.