The Barnaby Joyce citizenship crisis has sparked a diplomatic brawl between Australia and New Zealand, with Foreign Minister Julie Bishop declaring she would find it hard to trust a NZ Labour government if it had any role in trying to bring down the Turnbull government.

While New Zealand's Minister of Internal Affairs Peter Dunne has confirmed it was Fairfax Media's investigation that led to the discovery of Mr Joyce's dual citizenship and the subsequent political crisis, the Turnbull government has seized on claims that an Australian Labor figure made contact with a NZ Labour MP on the issue.

NZ Labour leader Jacinda Ardern confirmed on Tuesday that her frontbencher Chris Hipkins was involved.



"Yes, someone from the ALP put some legal question to him around citizenship. No mention was made of anyone's name, no rationale for any particular case being pursued was ever raised," Ms Ardern said. "He asked the questions without knowing how that might be used and has made it very clear, in hindsight, had he known how it would be used, he would not have asked the questions."

Mr Hipkins said he was not directed to ask a question on the issue, saying he submitted a question on notice into the NZ Parliament off his own bat because he too an interest following his conversation with an unnamed Australian Labor friend.