The Police Association is disappointed a report into the Roast Busters has laid the blame with the investigating officers.
An IPCA investigation found significant failings in the original police investigations into the group of 17 and 18-year-old men who boasted online about their sexual exploits with drunk and underage females.
Police began investigating the group in 2011 after girls as young as 13 complained they had been sexually violated, but no charges were ever laid because investigators believed there was no reasonable chance of a conviction.
Union president Greg O'Connor says it's too easy to blame the officers and a thorough investigation involving a fully resourced team for a year came up with the same result.
The IPCA's report says the investigating officers tended to approach each case on an individual basis instead of developing strategies to reduce the recurrence of what was "clearly unacceptable and, in some cases, criminal behaviour".
But O'Connor denies it's a performance issue and says it's about workload and resources.
"These are not slovenly officers who didn't care, they did care," Mr O'Connor told Breakfast this morning.
He said child protection teams are still being taken away to work on other inquiries and officers have to prioritise every day.
Police Commissioner Mike Bush said yesterday the standard of investigation in the Roast Buster cases fell far short of what he and the public expects.
However, Mr O'Connor says that statement was more about the commissioner's role.
"He's had a frozen budget for five years, he knows full well the minute he turns his back on the politicians he won't be the commissioner any more," he said.