The decision was made by police alone without his involvement, Mr Woodhouse said. He had sought assurances from Police Commissioner Mike Bush that the investigation had been thorough.
"This has been a very complex case and I have been assured by Commissioner Bush that a high priority has been placed on it and resources of both police and a number of other agencies have been committed to it.
"The priority always has been for the welfare of the young women and their families."
Asked if he was disappointed by the decision, he said: "It's not for me to be disappointed. What I want to be sure about was that a thorough investigation, considering all of the information available to police, has been undertaken, and I am satisfied that's the case."
He believed police had worked hard to ensure the women involved were supported, had the information they needed and were "protected" during the process.
"I'm satisfied they've done a very good job with that."
Asked if any further inquiries were warranted, he said he expected the second part of the Independent Police Conduct Authority investigation to be released in due course.
After police had digested the outcome of the investigation, they could consider whether anything further was required.
Green Party MP Jan Logie said the case showed there was an urgent need to overhaul the way sexual violence cases were dealt with.
"Many people will be disappointed that there is no justice for the victims in this case. The current system is not working. Too many victims are going without justice because of a systemic failure of our laws to provide for victims of sexual violence."
She said former Justice Minister Judith Collins had halted Law Commission work on processes for sexual violence cases and National had not gone ahead with a proposal for victims' advisers.
"It took two years and media attention for the police to even look at this case with any seriousness. This highlights a culture in which victims are not taken seriously."
Justice Minister Amy Adams said she had not read the report yet but anything to be learned from it would be taken seriously and feed in to ongoing work on how sexual assault victims were treated within the system and how it responded to them.
"Clearly one of the issues the system has to be set up well to deal with is to encourage victims to come forward and to feel supported through the system when they do.
"That's not a new issue. It's an issue we continue to work with. Partly you have to take into account the very fragile nature of the victims and the tremendous trauma they've been through.
"That puts them into a more vulnerable state in terms of their willingness to come through and how they will be affected by any perceived negative response or disbelief, if that is what they encounter."
She said there was a balancing act between protecting victims and ensuring the evidence was assessed fully so that only the guilty were convicted.
Calls for such cases to be handled under a non-adversarial system would not necessarily have meant a different result.
"In terms of the current report, the initial media reports suggests the issue was one of the evidence the police had to prosecute.
"Fundamentally you have to have a system where we can be assured the evidence is there to support a prosecution ... There would always have to be an standard of proof, an evidential burden that had to be met, and changing from one system to another isn't necessarily going to address the challenges met in this case."
Labour's acting deputy leader Annette King said she was concerned the mishandling of the case and outcome would put victims off reporting sexual crimes.
"This case has been mishandled from the start. That police have now decided -- after three years -- that they cannot prosecute anyone because of a lack of evidence must be hugely disappointing for the victims."
She said police and court processes already put some victims off reporting sexual abuse, and lessons had to be learned.
"New Zealanders' expectations would be that the handling of these cases will improve, not go backwards."
- Claire Trevett of the New Zealand Herald
