Rape victims say police are not taking their complaints seriously.

Some police officers are telling sexual assault victims that if their attacker claims it was consensual, charges are unlikely to be laid.

Several women spoken to by Stuff as part of an investigation into the way police handle sexual assault and rape cases say they were told in the early stages of the investigation that a denial by the accused was likely to prove fatal to a prosecution.

"They told me from the beginning if he chooses not to talk or says it was consensual then they couldn't press charges," said an Auckland professional, who says she was drugged and raped on a first date by a man she'd met on an internet dating site this year.

ROBERT KITCHIN/STUFF Rape complainants speak of re-victimisation and bungling investigations into their rape complaints.

She said there was other corroborating evidence.

"I felt like I wasn't being taken seriously, like the case had been written off before they'd even looked into it."

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Another victim, a grandmother, says a newly assigned investigating officer questioned the accused before even meeting her, and closed the case after finding his claims of consent "credible". That was ridiculous, she said, as she'd been accosted in her garden and the attacker fled afterwards.

She said she felt humiliated by the way police quickly closed the case in 2015.

The women came forward after police made the claim they had turned their attitude towards sexual violence cases around 10 years after the Commission of Inquiry sparked by the Louise Nicholas police rape allegations.

Police say they have ticked off all 47 recommendations in the inquiry report and now have more specially trained investigators and female staff.

But several of the victims who Stuff interviewed said they had been treated poorly by staff on designated sexual assault teams, including women. "You're either a cop who victim-blames or not, it has nothing to do with gender," one complainant said.

One woman said she had no communication from police for months, finally getting an email from a female officer saying the case was being closed and the accused was "trying to move on with his life".

Police national crime manager Detective Superintendent Tim Anderson said cases were assessed in their entirety and a suspect's statement was just one factor.

"I can assure victims that police take their complaints seriously and investigate all aspects fully."

A decision to prosecute was based on two main points – "evidential sufficiency" and public interest, he said.

Anderson urged anyone who believed their sexual assault complaint was not being taken seriously to email ASA@police.govt.nz.

Labour is promising a radical overhaul of the way the justice system deals with sexual assault and rape cases if it wins the election.

Associate justice spokesperson for sexual and domestic violence Poto Williams said only 13 per cent of the sexual assault cases reported to police ended in a conviction and something needed to be done to address the "power imbalance".

Labour would change the system so that a victim was believed as a starting point, and that an accused would have to prove consent – an idea rejected by National.

"That might cause some people difficulty but we have to do something about increasing the prosecution rates. There's no doubt sexual assault is a problem in our country," Williams said.

She wanted to see a "much more sympathetic" approach by the courts towards people who experienced sexual violence and police needed to be better resourced to investigate properly.