NSW Labor has secured the imminent release of the letter from Building Commissioner David Chandler, who tendered his resignation in June and will finish up in November.
The construction industry veteran was hired to clean up the state's building industry after a series of high-profile building defects were found, including at Mascot and Opal Towers in Sydney.
News Corp reports Mr Chandler cited a "problematic" relationship with former fair trading minister Eleni Petinos as one of the reasons he quit.
Ms Petinos was sacked from her portfolios 10 days ago by Premier Dominic Perrottet, amid allegations of bullying and an "unsafe" environment in her office.
Labor MP Courtney Houssos introduced a motion that passed parliament on Wednesday, that will ensure the resignation letter is publicly released within 24 hours.
All emails, texts and instant messages sent in the past eight months between Ms Petinos, her current and former staffers, former deputy premier John Barilaro and Mr Chandler will also be released.
The letter reportedly cites development company Coronation Property, where Mr Barilaro briefly worked earlier this year, as one of Mr Chandler's gripes.
Reports say Coronation Property hosted a meeting between Ms Petinos and Mr Barilaro on June 21, weeks before a building ban on a $500 million Coronation Property development was lifted.
Mr Perrottet told parliament on Tuesday he was not aware of the reports, had not read the letter, would seek advice and take action if required.
Labor Leader Chris Minns said he intended to ask the premier during question time on Wednesday about why he had not read Mr Chandler's resignation letter.
"Despite the fact that we've known about this resignation for weeks and weeks, (Mr Perrottet) informed the parliament that he had not read it," Mr Minns said.
"I'd encourage the NSW premier to examine that letter."
