Victoria's anti-corruption watchdog has warned that it can’t adequately investigate police misconduct because it has no powers to search or arrest potentially crooked cops, leading to some cases falling through the cracks.

In startling evidence given to state MPs behind closed doors, new IBAC commissioner Robert Redlich QC says this "extraordinary state of affairs" effectively allows suspects to lie to investigators, destroy evidence, or not provide a record of interview.

The pre-eminent former Victorian judge also condemned the culture of Victoria Police, where "loyalty to one’s colleagues (and) protecting the reputation of the human organisation gets precedence in some cases over doing the right thing."

IBAC Commissioner Robert Redlich QC

“Regrettably we know that in some cases, once we open up our information sources to Victoria Police officers, information does not stay with that person; it immediately ceases to have any level of confidentiality,” said Mr Redlich, a former Supreme Court judge and barrister.