Malcolm Turnbull has accused Bill Shorten and federal Labor of conspiring with the New Zealand Labour Party to undermine the government.
The prime minister told a coalition joint partyroom meeting in Canberra on Tuesday it wasn't surprising given Mr Shorten's record of "sneakiness, dishonesty and disloyalty".
'We have learned this morning the Australian Labor Party has been conspiring with the NZ Labour Party to undermine the position of the deputy prime minister and the government of Australia," Mr Turnbull said.
NZ Labour MP Chris Hipkins last week used a parliamentary question to quiz the NZ internal affairs minister on whether a child born in Australia to a Kiwi father would automatically have NZ citizenship.
Mr Hipkins confirmed he had asked the question after speaking with an ALP MP and was unaware of any issues around Barnaby Joyce.
The NZ internal affairs minister Peter Dunne on Tuesday rejected suggestions Mr Hipkins' question had instigated inquiries, which led to NZ authorities notifying Mr Joyce he was an NZ citizen by descent.
Rather, the inquiries were triggered by Australian journalists.
Mr Turnbull told the meeting Mr Shorten had "shown disloyalty all his life".
Mr Joyce said he found himself in a "ridiculous situation", made worse by Labor's "treachery".
NZ Labour leader Jacinda Ardern said any suggestion of a conspiracy was "false".
She said she had no knowledge of Mr Hipkins' question - which she described as "not appropriate" - and knew "absolutely nothing" about the Barnaby Joyce case until it broke in the media on Monday.
"I greatly value New Zealand's relationship with the Australian government. I will not let false claims stand in the way of that relationship."