The New Zealand MP responsible for setting in train the possible removal of Barnaby Joyce from Parliament was asked to raise the question of dual citizenship by the Australian Labor Party.
The revelation by NZ Labour leader Jacinda Ardern on Tuesday has outraged the Turnbull government.
“This is really borderline corruption in a sense,” junior minister Michael Sukkar told Sky News.
NZ Labour MP Chris Hipkins, in a parliamentary question last week, asked the internal affairs minister whether a child born in Australia to a Kiwi father would automatically have citizenship.
Ms Ardern said she’d since asked her MP why he asked that question.
“He’s been very clear: 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,” she told Radio NZ.
“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.”
The High Court has been asked to rule whether Mr Joyce’s NZ citizenship by descent made him ineligible for election to the Australian Parliament.
Mr Sukkar said the situation “stinks to high hell”.
“You’ve got an Australian political party working with a foreign political party to undermine our domestic government,” he said.
In a row that threatens to escalate in a tit-for-tat exchange between the coalition and Labor, the government is threatening to refer the eligibility of five opposition MPs – including Justine Keay, Susan Lamb and Tony Zappia – to the High Court.
“The Labor Party needs to produce the evidence or the government will obviously consider its options,” cabinet minister Christopher Pyne told ABC radio.
Labor insists it has rigorous vetting processes in place for candidates.
Opposition frontbencher Tony Burke said no one was allowed to lodge a nomination as a candidate until the “cumbersome process” was finished.
Prime Minister Malcolm Turnbull is also under pressure over comments he made in parliament about the likely outcome of a High Court ruling.
He argued the court “will so hold” Mr Joyce’s right to sit in parliament.
Shadow attorney-general Mark Dreyfus questioned whether Mr Turnbull understood the independence of the judiciary.
“These were the comments of an arrogant prime minister who came perilously close to directing the High Court,” he told ABC radio.
Attorney-General George Brandis denies Mr Turnbull was telling the court what to rule.
Mr Pyne said the court would make its own decision based on the evidence presented to it.
“I’m sure it won’t be reading Hansard,” he said.