Ms Collins said she was taking the step because she had previously advised people that if they had complaints about police handling of matters they should take them to the IPCA, and if the requests were turned down then as Justice Minister she should ask why.
Labour has called on the Government to urgently set up a public inquiry into the Rewa case after Third Degree reported there had been a chance for police to arrest him at the start of his crime spree.
Police failed to check the alibi given by Rewa after the first of those attacks, according to third Degree.
Rewa went on to attack 24 other women in nine years, including the rape and murder of Susan Burdett in her Papatoetoe home in 1992. Teina Pora was convicted in the Burdett case.
Labour's justice spokesman Andrew Little said there was now "serious and credible evidence that the investigations that led to Teina Pora's prosecution and into the Malcolm Rewa case are highly questionable".
"An independent public inquiry into all aspects of the Rewa and Teina Pora cases is needed to restore public confidence," he said.
"It's not enough for the minister to just say the Independent Police Conduct Authority can investigate given that they declined to do so, and that it is probably beyond their resources anyway.
"There are 24 victims, one dead, with a real possibility they may have been spared their tragedy if police had acted properly on information available."
Speaking to reporters at Parliament later, Ms Collins said she was was not told before last night's programme that the IPCA had declined to investigate the complaint.
"As the minister with responsibility for the IPCA, I thought I would have actually known about that matter before it was made public.''
Ms Collins said while the IPCA was an independent body and she could not direct it, it was appropriate for her to find out the reasons it could not investigate, particularly as she had said it was the correct body.
If it was not, she would seek advice on whether anything could be gained for the victims and whether it should be taken further.
"I'd look at the law and I'd look at the facts that were known to me. It's not a decision I think we should make on the hoof,'' she said.
Ms Collins said if she was in the same position as the victims, she would be seeking answers too.
Police Association president Greg O'Connor said there were aspects of the police handling of complaints about the Rewa case "that would certainly not fit with the standards of policing we expect today''.
Mr O'Connor said he had yet to look into the claims the IPCA had declined to look into a complaint.
"The Police Association did request an inquiry [into the Pora case] and certainly we believe that that's where we should be now.
"I have sympathy for the [police] commissioner and sympathy for the minister on this one because now it's before the Privy Council, that essentially will be the inquiry.
"We can hope that now there is going to be a forum for the facts that need to come out.''
"You've got to be careful basing everything on one television programme,'' Mr O'Connor said.
"Experience has shown that everything has got to be put in context and sometimes things are put out of context.''
The Police Association's position remained that there should be an inquiry into the Pora case, Mr O'Connor said.
"In relation to Rewa, it's a different set of circumstances. We're looking at a historical event which clearly has got disturbing implications.
"However, Mr Rewa is in prison and fortunately is likely to remain there for some time.''
"When the police association asked for an inquiry, we essentially thought it should come from the minister, at that stage it wasn't before the Privy Council, now of course things are underway, the minister's hands are certainly tied.''
