Premier Gladys Berejiklian on Saturday said she'd spoken to Mr Maguire and he advised her of his intention to resign before parliament resumes on August 7.

"I accepted that," Ms Berejiklian told reporters in Sydney.

Mr Maguire quit the Liberal party and his role as a parliamentary secretary a week ago after a corruption inquiry heard secret recordings of him, with a local councillor, discussing potential commissions from property deals with a wealthy Chinese developer.

Despite mounting pressure he had - until Saturday - refused to quit as an MP, instead announcing he wouldn't recontest the next state election in March 2019.

Ms Berejiklian said she and deputy premier John Barilaro had agreed the Nationals wouldn't run in the upcoming Wagga Wagga by-election.

"There will not be a three-cornered contest," the premier said on Saturday.

"The Liberal Party's held that seat for half a century and the Liberal Party has opened nominations."

Mr Maguire has apologised for causing "distress and embarrassment" after conversations recorded in 2016 were played to the Independent Commission Against Corruption.

He was heard boasting about clients with "mega money" to the Canterbury City Councillor at the centre of the investigation.

Mr Maguire on Monday said he'd continue to serve on the crossbench until the next election as he didn't want to burden taxpayers with the cost of a by-election.

But on Wednesday Labor warned that if Mr Maguire didn't quit before parliament resumed the opposition would move a rarely-used motion to try and force the former junior minister out.

"The only reason Mr Maguire is leaving parliament is that Labor was moving to expel him," Opposition leader Luke Foley said in a statement on Saturday.

"The premier sat on her hands and did nothing to force him from parliament. She was weak."

Mr Foley said ALP candidate Dan Hayes would run in the upcoming by-election.

Mr Maguire two days ago requested privacy following the death of his son-in-law after a short illness.

Australian Associated Press