The revelation comes just a day after allegations that The Star casino at Pyrmont, which sits outside the lockout zone and is therefore exempt from the restrictions, is under-reporting the number of assaults at the venue.

The director of the NSW Bureau of Crime Statistics and Research, Don Weatherburn, revealed the new analysis to Fairfax Media, which was underway before the allegations against the casino surfaced.

Dr Weatherburn said the public debate around the 1.30am lockout and 3am last drinks laws has proceeded with the understanding that reviewing them once was sufficient.

However, he said it was important to continue to review their impact as drinking habits and other factors change.

"It's not as if this question has one answer," he said. "We think that until the situation fully stabilises we should be adding new data and repeating the analysis.

"We have to keep taking snapshots as to what's going on to get a fuller appreciation of the effect of the lockouts."

The bureau has previously found there was a 45 per cent drop in assaults in Kings Cross and 20 per cent in the Sydney CBD in 16 months after the laws were introduced in February 2014.

Dr Weatherburn said he expected the fresh analysis to be ready by mid-2017.

It comes as the Baird government is preparing to respond to a September report on the laws by former judge Ian Callinan.

The statutory review found that the laws remain valid but suggested a 2am lockout and 3.30am last drinks in venues with live entertainment could be trialled for two years.

The allegation against The Star – which is denied by the casino operator – emerged on Monday night in a leaked internal document prepared by the NSW liquor and gaming regulator.

The report examined the number of violent incidents at The Star between March and August this year.

It said 75 of the 111 violent incidents during the period – or 67 per cent – "did not result in police attendance despite the severity of the incident involved or the injuries caused to the parties".

Dr Weatherburn said if there was under-reporting it might have affected the bureau's analysis of whether violent incidents have been pushed outside the lockout and last drinks zone.

In April, the bureau published a report that said the number of non-domestic assaults recorded at The Star increased after the lockout laws were introduced but noted: "In absolute terms, the increase was fairly small; slightly less than two additional assaults per month."

Dr Weatherburn said if The Star has been under-reporting assaults since the lockout laws began "then we will have perhaps seriously underestimated the displacement to The Star casino".

The bureau will now examine every violent incident recorded at The Star – potentially dating back to the inception of the lockout laws – to see if there has been a decline in reporting by its staff.

A decline in staff reporting of incidents relative to reporting by the public could indicate a shift to deliberate under-reporting by the casino.

A spokesman for The Star has said it "rejects the [leaked internal] report as it contains inaccurate information, a misunderstanding of the incident reporting process at The Star and expresses significantly misplaced concerns that reflect a lack of understanding of The Star's business".

Paul Newson, deputy secretary of liquor, gaming and emergency management at the Department of Justice, has said the internal report "was prepared to assist ongoing discussions with the casino operator, and was the first step in an ongoing dialogue to better understand existing reporting arrangements and identify any potential gaps".