The NSW opposition will seek the release of a resignation letter from the state's building commissioner, who left his post shortly before the minister he reported to was sacked.
David Chandler announced his resignation in July, having been the commissioner since the role was first created in 2019.
His exit came after his contract was extended to September 2023, and after former fair trading minister Eleni Petinos requesting an internal probe into whether he had misled parliament.
A video emerged of Mr Chandler telling builders he'd given banks an "informal list" of certifiers he would not employ, despite earlier telling a parliamentary committee it was not his role to recommend specific building certifiers.
Following Mr Chandler's resignation, about a month after the video was reported in The Australian, anonymous bullying allegations soon emerged involving Ms Petinos.
After initially defending the junior minister, Mr Perrottet booted her from cabinet after receiving further information about her alleged conduct, which has not been made public.
Labor's better regulation spokeswoman Courtney Houssos says she will move a motion in the upper house on Tuesday for Mr Chandler's resignation letter to be released.
"I haven't read that letter," Mr Perrottet told question time, adding that was proof it had nothing to do with Ms Petinos' sacking as a minister.
"I made that decision and I stand by that decision," the premier said.
Ms Houssos says Mr Chandler's premature and abrupt resignation raises further questions about Ms Petinos' conduct as a minister.
"The premier hasn't even read the letter despite these questions," she said.
"We need to get to the bottom of it so I'm calling on the premier again to release the letter."
Ms Houssos will move a motion in the upper house to produce the resignation letter within 24 hours.
"It should be a relatively easy document for the government to produce," she said.
Ms Houssos also questioned Ms Petinos' attendance at meetings with a property group linked to former deputy premier John Barilaro, revealed in ministerial diaries published on Monday night.
Ms Petinos met twice with Coronation Property Co to discuss "fair trading building related matters" on June 2 and June 21.
"This was a minister who it took months of pleading from the Mascot towers owners to meet with, but in the space of several weeks she made time to meet with the Coronation group that employed the former deputy premier," Ms Houssos said.
Mr Barilaro told the Daily Telegraph he was only present for the second meeting, when he was no longer an employee of the group, and attended socially to celebrate his appointment to the overseas trade role he resigned from nine days later.
