The resignation letter of former NSW Building Commissioner David Chandler was sent to Dominic Perrottet's chief of staff four hours before the premier announced he had sacked a minister referenced in it, newly revealed documents show.
Mr Perrottet said he had not read the letter before sacking Ms Petinos and it was not the reason he did.
Department of Premier and Cabinet secretary Michael Coutts-Trotter was informed of Mr Chandler's resignation when his letter was given to Department of Customer Service secretary Emma Hogan on July 7.
Ms Hogan also sent Mr Chandler's resignation letter to Mr Coutts-Trotter and the premier's chief of staff, Bran Black, at 4pm on July 31.
A statement from the premier announcing the sacking of then fair trading minister Eleni Petinos was sent out four hours later, after "further matters concerning her were brought to (his) attention".
He had previously defended Ms Petinos after bullying allegations emerged from her office in the days prior.
Mr Perrottet said the decision to sack her came after a discussion he had with Ms Hogan.
"The principal purpose of that discussion related to staff matters," he told parliament on August 11, the day the letter was made public.
He was also advised "appropriate action" had been taken with regards to the matters raised in the letter, which was "peripheral" to the discussion.
He had not read it before sacking Ms Petinos, or a day later when Ms Hogan sent it off to the Independent Commission Against Corruption.
"That was the appropriate decision for her to make," Mr Perrottet said.
Mr Perrottet received and read the letter the day before it became public, though he told parliament it was "irrelevant" when he had read it.
"What is relevant is that appropriate action had been taken," Mr Perrottet said.
Asked to advise the house why he sacked Ms Petinos, Mr Perrottet said the question was "ridiculous", and he had already answered it numerous times.
"I had a discussion with the department secretary on (July 31) about the issues in the workplace of the former minister. I made the decision to change the ministry based on those discussions," he said.
Labor's better regulation spokesperson Courtney Houssos said on Friday it was not believable that Mr Chandler's resignation letter played no part in Ms Petinos' sacking.
"What we learnt today is that the premier's own chief of staff received it on the same day that Ms Petinos was sacked and the day before it was referred to ICAC," Ms Houssos said.
"It just isn't believable that it took another 10 days for the premier to be briefed on its contents."
Mr Chandler's letter noted a problematic relationship between him and the minister and raised concerns over a relationship between Ms Petinos and the Coronation Property Group, which briefly employed former deputy premier John Barilaro.
Mr Barilaro met with Mr Chandler in May to discuss a stop work order issued at the group's Merrylands development, which was lifted in July, three days before Mr Chandler sent his resignation letter.
Ms Petinos met with Coronation twice in June, according to ministerial diaries.
Mr Barilaro was at the second meeting on June 21.
The former Nationals leader told News Corp Australia he attended socially to celebrate his recent and brief appointment to an overseas trade role, which he resigned from within two weeks of it being announced.
His appointment remains the subject of multiple inquiries and separately led to senior government minister Stuart Ayres resigning after more than eight years in cabinet.
