An integrity commissioner has acted as prosecutor, judge and jury in going after the devastated former chairman of Racing Victoria over a cobalt investigation leak, a court has heard.

David Moodie admits telling his racehorse trainer Peter Moody about a rumour two other trainers also had positive cobalt results but denies that compromised the investigation or that he misled the Racing Victoria board.

Racing Integrity Commissioner Sal Perna was determined to find Moodie guilty of something, the Victorian Supreme Court heard on Monday.

Moodie's barrister Simon Wilson QC said Mr Perna exceeded his powers in making the findings, as he received a referral into the leak rather than a complaint.

"This former policeman has gone on an absolute frolic of his own in terms of enlarging it, no doubt perhaps to justify his position or show how important he is," Wilson said.

Perna turned a simple request for information into a prosecution of Moodie, Wilson said.

"He became judge and jury himself - prosecutor, judge and jury."

Moodie has been devastated by Perna's report and the prominent racehorse owner has not been on a racetrack for months, Wilson said.

"His family's upset. He's upset," Wilson said.

"It's had a devastating effect on him personally."

Perna determined Moodie, then an RV board member, was not the original source of the January 2015 leak about positive cobalt swabs for horses trained by Mark Kavanagh and Danny O'Brien.

But his December 2016 report found Moodie inappropriately disclosed information to Moody, compromising or potentially compromising the investigation's integrity, and misled the Racing Victoria Integrity Council and the RV board about it.

Wilson said Moodie was concerned about Moody's welfare after the trainer's own positive cobalt swab and attempted to console him by telling him about a rumour a couple of others also had cobalt positives.

Wilson said Moodie did not name the two trainers, but admitted that describing one as Moody's best mate at Flemington could have identified O'Brien.

Wilson said Moodie contacted then RV chief executive Bernard Saundry after hearing the rumour from a newspaper reporter.

Moodie, who stood down during Perna's investigation and agreed to resign after the report, asked Justice Kevin Bell to overturn the commissioner's findings.

Perna's barrister will outline his response on Tuesday.