NSW Premier Gladys Berejiklian's political opponents want a corruption watchdog to investigate allegations that former Wagga MP Daryl Maguire was able to travel overseas without her formal approval.
One Nation MLC Mark Latham has said he will refer the allegations to the Independent Commission Against Corruption (ICAC) and the Labor opposition has said it will support the referral.
ICAC this year heard testimony and phone calls detailing how Mr Maguire visited the Solomon Islands, Samoa and Papua New Guinea in 2017 and 2018.
Mr Latham said documents related to Mr Maguire, which were demanded by the NSW Upper House, had not included any requests for him to travel in the South Pacific.
"The ministerial guidelines say that parliamentary secretaries need to get approval for the premier to travel overseas for business-related trips," Mr Latham said.
"Even though he had applied to Premier Mike Baird in 2014 and 2016 for approval for overseas trips, he didn't make any application for approval when Gladys Berejiklian was Premier."
The South Pacific travel took place during a period that Mr Maguire and Ms Berejiklian were in a "close person relationship" according to their testimony at ICAC.
"It's inconceivable given they said they were in a close personal relationship that she didn't notice he was overseas," Mr Latham said.
The Premier's office did not respond to a request for comment.
Opposition treasury spokesperson Walt Secord said Labor will support Mr Latham's referral to ICAC.
"We believe Mr Maguire and the Premier have serious questions to answer and there is an absolute lack of documentation, a suspicious lack of documentation," he said.
"They should answer these serious questions under oath so there is no dodging them like at a press conference or sweeping the allegations away.
"That is why we are supporting this course of action."
When appearing before ICAC in October, Mr Maguire agreed with a statement that his travel during that period was "not in any official capacity" but also agreed that his position in Parliament was "something in the nature of a door opener in the South Pacific region".
Mr Maguire's electorate officer told the federal Department of Foreign Affairs and Trade via email in April 2017 that "although [Mr Maguire] is a member of parliament, that is not the main capacity in which he is travelling to Samoa".
Mr Latham said it appeared that ICAC did not have a full understanding of Ms Berejiklian's role in approving overseas travel when she as witness in October.
ICAC heard testimony that Mr Maguire sought a memorandum of understanding between the Samoan government and Chinese investors about a potential new casino as part of his travel in the South Pacific.
Mr Secord said it "does not pass the pub test" that Ms Berejiklian "was unaware her then boyfriend or partner was going overseas to Papua New Guinea, the Solomon Islands and Samoa".
"I would know if my partner was overseas, and that's why we want her to answer questions under oath," Mr Secord said.