The chief of staff to NSW Premier Gladys Berejiklian had to effectively order backbencher Daryl Maguire to "cease and desist" as he threatened to fly to China the same time as an official trade mission, a corruption inquiry has heard.
Sarah Cruikshank initially thought it was "ridiculous" that Mr Maguire would head to Shanghai over a business deal involving a southern NSW dairy, she told the NSW Independent Commission Against Corruption on Friday.
She recalled quickly moving to stop the trip but said she was unaware Mr Maguire harboured a desire to join the board of one of the dairy's owners, UWE.
Had she known that information, she'd have reported the then-Wagga Wagga MP to the anti-corruption commission immediately, she said.
"I mean, it's pretty serious," she said.
The inquiry is investigating whether Mr Maguire, Wagga's MP from 1999 to 2018, breached public trust by using his public office and parliamentary resources to improperly gain a benefit for himself or for G8way International - a company he "effectively controlled".
In an August 2017 letter marked "urgent" and written on NSW parliamentary letterhead, Mr Maguire wrote to the chairman of the board of Chinese firm Bright Food over its interest in dairy facilities in Leeton.
Bright Food had delayed the sale of its controlling stake in a joint venture with local firm UWE.
Mr Maguire said failure of the venture would raise "very serious questions by our government ... about future joint ventures with Chinese companies".
"In order to avoid this potential embarrassment, I will fly to Shanghai to meet with you face to face in a genuine effort to resolve this pending crisis," he said.
Charlie Cull, then former policy adviser to then trade minister Niall Blair, learnt of the issue when copied into an email of the letter.
"I thought it was an appalling letter and provocative," he said.
With Mr Blair also due to travel to China on an official trade mission in September 2017, Mr Cull feared Mr Maguire could embarrass the minister and the state of NSW.
He started trying to discourage Mr Maguire from travelling, the inquiry heard..
"Initially I raised it with him over the phone and eventually we got the premier's office involved," Mr Cull said.
Ms Cruishank couldn't recall how the message of "cease and desist" was communicated to Mr Maguire but suspected it wasn't over a phone call.
Any reaction by Mr Maguire would have been memorable, she said.
Notifying the premier beyond "head's up, Daryl's being annoying" was unlikely, Ms Cruishank said, as she thought it was a "low-level" issue.
Ms Berejiklian is due to give evidence on Monday.
Mr Maguire will also give evidence next week.
The inquiry is investigating whether Mr Maguire's activities amount to the criminal offence of misconduct in public office.
The former NSW member for Wagga Wagga sat in parliament for 19 years before his resignation in 2018, after a separate ICAC inquiry heard he sought payment to help broker deals for property developers.