An extra 1500 NSW police officers will be recruited over the next four years in a bid to battle “frontline” crime, child-sex crime and elder abuse.

Premier Gladys Berejiklian and Police Minister Troy Grant made the announcement alongside Police Commissioner Mick Fuller on Tuesday.

The increase comes after sustained lobbying by the Police Association, which has been warning that high-risk sex offenders could fall through the cracks and detectives could be overworked unless 2500 new officers are recruited.

Ms Berejiklian said the commitment, four months out from the NSW election, was the biggest investment in police numbers in more than 30 years.

It is estimated to cost more than $580 million.

Each area command will have at least one extra officer dedicated to monitoring people on the child protection register as well as elder abuse.

Mr Fuller says the extra numbers doesn’t mean NSW Police will drop its entry standards.

“We have consulted widely in terms of where we need to put those resources, including the NSW Police Association,” he said.

“Over the four years, with the flexibility that I’ve been given as the commissioner, we will continue to move resources around to make sure the people of NSW are safe.”

Despite the Police Association earlier this year calling for 2500 extra police, president Tony King said he was pleased with the commitment.

“I’m pleased to be able to say the government has listened,” Mr King told reporters.

In a statement Mr King said the largest injection of new recruits in decades would fill “critical gaps” in the force.

Earlier this year the union released a paper outlining issues caused by under-resourcing and called on all parties vying to win next year’s state election to fix them.

The Back the Blue document proposed taking prisoner transport duties off police and put it onto Corrective Services, as well as higher-powered weapons and equipment to deal with terrorist and high-risk incidents.

It noted NSW Police had been unable to reach response time targets for years and “overworked” police were “feeling helpless”.

The gaps were particularly risky when it came to monitoring pedophiles and sex-offenders, who require supervision once released into the wider community.

“Without more officers, the capacity to properly supervise every offender will be seriously compromised, putting children directly at risk,” the document said.

But Opposition Leader Michael Daley questioned the timing and the figures of the announcement.

“Now on the eve of an election the government have decided to beef up police numbers. Well, the Police Association have been calling for the government to do this for eight long years,” Mr Daley said.

He said the costing of the commitment “don’t add up” and asked the premier to submit the policy to Treasury for costing.

-AAP