After an extraordinary bombshell 24 hours earlier, Barnaby Joyce has confirmed he is no longer a New Zealand citizen.

The Nationals leader told Parliament he had received verbal confirmation before Question Time that his application to renounce his NZ citizenship had been accepted.

He is now awaiting documentation.

It comes as New Zealand Labour leader Jacinda Ardern hit back at Foreign Minister Julie Bishop for making "false claims" about the NZ Labour Party.

In a strongly-worded statement, Ms Ardern said she will meet with the Australian High Commissioner later today to "register my disappointment".

Ms Bishop told reporters in Canberra it would be "very difficult to build trust" with a Labour government should the opposition party win the upcoming New Zealand election, which will be held on September 23.

Ms Ardern said it was "highly regrettable" that Ms Bishop had chosen to make "false claims" about the New Zealand Labour Party.

"I have been utterly transparent about the situation. I stand by my statements that I knew absolutely nothing about the Barnaby Joyce case until it broke in the media yesterday afternoon," Ms Ardern wrote.

"I had no knowledge about the parliamentary questions lodged by Chris Hipkins MP. I have also been clear that those questions were not appropriate."

Ms Ardern said she would "happily" take a call from Ms Bishop to discuss these matters.

I value our relationship with the Australian Govt highly. I won't let disappointing & false claims stand in the way of that relationship

— Jacinda Ardern (@jacindaardern) August 15, 2017

Ms Bishop today accused the Labor Party of compromising relations between Australia and New Zealand, saying it would be hard to develop a relationship with members of a party that had been "used by the Australian Labor Party to seek to undermine the Australian government".

She slammed Opposition leader Bill Shorten for "treachery" in a spirited press conference after revelations a Labor MP prompted a New Zealand Labor MP to probe Barnaby Joyce's citizenship status.

"Bill Shorten has sought to use a foreign political party to raise serious allegations in a foreign Parliament designed to undermine confidence in the Australian Government," Ms Bishop told reporters in Canberra.

"Bill Shorten has serious questions to answer.

"This is highly unethical, at least.

"But, more importantly, puts at risk the relationship between the Australian Government and the New Zealand Government."

She called on Mr Shorten to reveal the name of the MP who spoke to New Zealand Labor.

"We're used to the dodgy backroom deals from Bill Shorten when he was leader of the union movement - he's now brought that not only into Australian politics but now into the international politics."