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, documents reveal.

Department of Premier and Cabinet secretary Michael Coutts-Trotter was informed of the resignation when Mr Chandler’s letter was given to Department of Customer Service secretary Emma Hogan on July 7.

Documents which NSW parliament ordered be released show 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 announcing the sacking of then fair trading minister Eleni Petinos was sent out four hours later.

Mr Perrottet said he spoke to Ms Petinos “after some further matters concerning her were brought to my attention”.

“Ms Petinos’ service as a minister will cease with immediate effect,” he said.

The premier had previously defended Ms Petinos after bullying allegations emerged from her office in the days prior to her sacking.

However, Mr Perrottet did not read the resignation letter before sacking Ms Petinos or before it was referred to the Independent Commission Against Corruption on August 1, he told parliament earlier this month.

He said that was proof it had nothing to do with her sacking.

Employee Relations Minister Damien Tudehope, and Ms Petinos, similarly said they had not read the letter in the days before it was made public.

As the letter became public on August 11, Mr Perrottet said it was “irrelevant” when he had received and read it, which was the day before.

The matters raised in the letter were “peripheral” to the ministerial sacking.

“It was not relevant at all to the decision that I made,” he told parliament.

Mr Chandler’s letter raised his concerns over the relationship between Ms Petinos and the Coronation Property Group, which briefly employed former deputy premier John Barilaro.

Mr Barilaro also 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.

Opposition Leader Chris Minns says the premier has serious questions to answer.

“For weeks we’ve been told there was no link between the government receiving the building commissioner’s resignation letter and the sacking of Eleni Petinos,” he said.

Labor’s better regulation spokesperson Courtney Houssos said it was not believable the premier did not know the contents of the letter, which had been ringing alarm bells internally since July 7, when he sacked Ms Petinos.

“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 Perrottet’s office has been contacted for comment.

– AAP