New South Wales Environment Minister, Robyn Parker has defended herself by criticizing the delays in informing her office about the deadly toxic cloud leaked from the Orica plant at Newcastle, telling Parliament the delay was "a matter of concern".

The Environment Minister was questioned about government's slow response to the two hexavelent chromium leaks from Orica's Kooragang Island ammonium nitrate plant on August 8. Government has been heavily criticized for taking three days to inform the public about the dangerous gas leaks.

Parker told Parliament that Orica alerted her department at 10.30 am on Tuesday and that existing legislation only requires the company to do so "as soon as practicable".

The Minister also reiterated that her office has only informed by the Office of Environment and Heritage via an email at 4.23 pm on Wednesday a day after the department was notified of the leaks by Orica.

''I'm not on this email list and I did not receive the email,'' she said. ''This delay is a matter of concern to me''.

She said that she had been informed that Orica had begun informing residents at 6.15 pm by her chief of staff, more than two hours after her office received the notification.

"I was told that Orica were out door-knocking, in other words the community were being told," Parker said in a report from ABC News.

"I was told that that the Office of Environment and Heritage, the regulator, were on the ground, Orica had been shut down, processes were in place.

"And that the chief health officer, who's responsible for the health response, was there."

"'All of the advice that was given to me at that time was that everything that needed to be done, was being done,'' the minister said.

Parker accused the Opposition Leader, John Robertson of ''scaremongering and frightening people'' over the leak.

Robertson replied that the Environment Minister was missing the point and that she should have told Stockton residents about the leaks as soon as she found out.

The Minister directed criticism for delays back at Orica.

"Where was Orica's disaster plan, why wasn't there an immediate call?" she asked.