Figures released by the Bureau of Crime Statistics and Research on Monday show the adult jail population fell from a record high of 10,822 in April to 10,515 in June, a reduction of more than 300.

The bureau said that the drop was mainly attributable to a reduction in the number of defendants being held on remand awaiting trial.

In June, the Baird government bowed to pressure from victims groups and some sections of the media and announced a review of the state's new bail regime after just four weeks.

The new laws, which started on May 20, replaced a complex series of presumptions against bail for certain offences, such as murder, with a broad consideration of whether the accused posed an "unacceptable risk" of reoffending.

Critics of the new Bail Act have pointed to a handful of controversial decisions as proof the laws were allowing criminals to "walk free" and should be amended.

But the review was condemned by the legal profession as "premature and misconceived".

Bureau director Don Weatherburn said the fall in remand numbers in NSW coincided with the introduction of the new bail laws "but the precise reason for the fall is not yet clear".

“There are three possibilities," Dr Weatherburn said. "The first is that courts are granting bail to a higher proportion of defendants.

"The second is that the arrest rate for serious offences is falling.

"The third is that police are more often dispensing with any requirement for bail.

"We will have a clearer picture of which of these is true by September.”

The number of people sent to jail due to police refusing bail fell by 58 per cent between February and June this year, the bureau said, while the number of people sent to jail because the court refused bail fell by 40 per cent in the same period.

It is understood former Labor government attorney-general John Hatzistergos, who was asked to conduct the urgent review of the bail laws and recommend "potential enhancements", handed his report to the Department of Premier and Cabinet on Friday.

He was widely expected to recommend that some of the presumptions against bail in the old laws be reinstated.

NSW Bar Association junior vice-president Arthur Moses, SC, said a Law Reform Commission review of the state's bail laws - which led to the new regime - highlighted the growing population of people in custody awaiting trial.

The remand population increased by 69 per cent between 2000 and 2010.

"During this period, there was an increase in the amount of persons of Aboriginal background and vulnerable persons who were being kept in custody awaiting trial," he said.

"The figures demonstrate that approximately 50 per cent of persons who are charged are ultimately acquitted or do not receive a sentence of imprisonment if convicted."

Attorney-General Brad Hazzard said that Corrective Services was managing the prison population effectively and there was "nothing new" in the fluctuation of prisoner numbers.

“Prison numbers have historically risen and fallen for a complex range of reasons,” Mr Hazzard said.

“In the past six years, the average prison population in NSW has been above 10,000 for four of those six years."

But he said the figures would be incorporated into the Bail Act review.

“The NSW government announced the review of the Bail Act last month because the Premier and I were concerned some recent bail decisions did not reflect the government’s intention to put community safety at the forefront of all bail decisions,” Mr Hazzard said.

He said if Mr Hatzistergos found changes needed to be made to the laws, the government "won’t hesitate in doing so".