The Prime Minister's standing by her remark about National's leader and the Serious Fraud Office.

Judith Collins wants Jacinda Ardern to "correct the record" after calling it 'interesting' National wants to double the SFO budget, commenting Collins "has a little history with the SFO".

An inquiry cleared Collins of any inappropriate action.

However, Ardern told The Country it was just a statement of fact.

"In the leader of the Opposition's history, she has a resignation that was in relation to the SFO. That was simply my reference."

Meanwhile, Ardern confirmed that Australia could open up to New Zealanders, before Australians are allowed to come here.

An Australian taskforce has unveiled plans to establish a trans-Tasman bubble by November, and start lifting state border restrictions by early December.

But Aussies may not be allowed into New Zealand until early next year.

"There is every chance that the Australians could just decide that they want to open up to New Zealand reagrdless of whether we're opening to them, and that is absolutely their prerogative."