Police in New South Wales have begun using new powers to issue on-the-spot apprehended violence orders (AVOs) in domestic violence cases.

Emergency Services Minister Stuart Ayres says under changes to the law, officers can also direct alleged perpetrators to leave the family home and if necessary detain them for up to two hours to allow an Apprehended Domestic Violence Order (ADVO) to be served.

"This will reduce the risk of defendants fleeing before the order is served and will enable victims to safely remain in their home, rather than having to seek emergency shelter," he said.

The changes, which came into force last week, are part of the NSW Government's Domestic Violence Justice Strategy, which aims to improve the way police and the legal system respond to domestic violence.

Nearly 45,000 ADVOs were issued in NSW last year.

Eighty per cent of those cases occurred outside of normal business hours, resulting in delays while police tracked down an on-call magistrate.

The NSW Police spokesman on domestic violence, Assistant Commissioner Mark Murdoch, says that process has now been streamlined.

"Previously a police officer would have to make an application to an authorised Justice and the Justice would have to authorise the order," he said.

"Now police at or above the rank of sergeant will have the ability to fulfil the role."

The changes only apply to domestic violence cases and defendants will still need to appear before a local court within 28 days. The accused can then make an application to challenge or vary the ADVO issued by the police.

Interim or final ADVOs will only be issued by a magistrate.

Domestic violence advocates cautious about changes

Domestic violence advocates have broadly welcomed the changes but are concerned that police may lack the specialist training required to deal with complex domestic violence cases.

Domestic Violence NSW project manager Moo Baulch says it can sometimes be hard to identify the primary perpetrator.

"We know, for example, that there are an increasing number of victims who have ADVOs taken out against them because perpetrators are getting clever at convincing police that they are the victim," she said.

"For vulnerable and high-risk victims such as people with intellectual disabilities, mental health issues, same-sex and lesbian, gay, bisexual, transgender, intersex and queer (LGBTIQ) couples and people whose first language is not English, police may struggle to accurately identify the dynamics of the abuse."

Women's Legal Services NSW says it welcomes any improvements that result in speedier protection for victims but it voiced reservations about the expanded police powers.

Principal solicitor Janet Loughman says monitoring how the new provisions work in practice will be important.

"While we understand why the police have been provided with additional powers to give directions to ensure defendants are served more quickly with the necessary documents, we do not support the removal of judicial oversight in the issuing of provisional AVOs," she said.

"Provisional orders should be made by authorised officers."

See more on this story on the NSW 7pm News, on ABC News 1.