The ICAC wants the NSW government to restore its powers, saying last week's landmark High Court ruling could kill off investigations and compromise criminal proceedings.
The highest court in the land ruled on a 4-1 majority the ICAC was unable to continue its controversial investigation into senior prosecutor Margaret Cunneen.
The decision was a major blow to the corruption watchdog which took five days to publicly respond to the humbling defeat.
The body has put pressure on the state government to amend the ICAC Act "as a matter of priority" in relation to the definition of "official misconduct", and for the changes to be applied retrospectively.
But the man who founded ICAC said it had acted beyond its intended powers and had misread the legislation.
"This was a phenomenal misuse of their powers when this could have very easily been investigated by the police," Professor Gary Sturgess told AAP.
"I think they're probably a bit bruised and surprised that they're not quite the heroes anymore."
The ICAC says it will be unable to report on several current operations after the High Court ruled its allegations against Ms Cunneen did not amount to corrupt conduct and the watchdog had no power to investigate her.
The ICAC accused the top silk of perverting the course of justice by advising her son's girlfriend, Sophia Tilley, to fake chest pains at a car crash scene in May 2014 to avoid being breath tested.
"The (High Court) decision ... will severely restrict its ability to report on Operations Spicer and Credo," the ICAC said.
Operation Credo examined the Eddie Obeid-linked Australian Water Holdings while Operation Spicer's investigations uncovered the depths of the donations scandal which rocked the NSW Liberal Party.
Those two ICAC probes have so far claimed a number of Liberal scalps, including former NSW premier Barry O'Farrell and federal assistant treasurer Arthur Sinodinos.
Prof Sturgess said the High Court decision would most likely impact those on the margins of Operation Credo.
ICAC argued the High Court ruling had the potential to result in "costly and protracted litigation" with people involved in corrupt conduct findings.
"One of the problems of ICAC is that it's very powerful and has been highly regarded and has done some good work," Prof Sturgess said.
He said Ms Cunneen was "feisty" to take on ICAC.
"I know of other people who...weren't prepared to challenge," he said.
Premier Mike Baird's office is digesting the ICAC's response and will make an announcement "in due course".
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