Anti-gambling campaigner Tim Costello has called on the Victorian Government to force James Packer to reduce his stake in Crown's gambling licence, after the casino was fined $300,000 for illegally altering buttons on poker machines.

Key points: Buttons concealed so only minimum and maximum bets were available

Buttons concealed so only minimum and maximum bets were available Crown fined $300k, told to update its compliance framework

Crown fined $300k, told to update its compliance framework Regulator said staff did not believe approval was needed to cover buttons

The Victorian Commission for Gambling and Liquor Regulation (VCGLR) penalised Crown with the fine and a letter of censure, after it found blanking plates were placed over certain buttons on 17 poker machines in the Melbourne casino last year.

Mr Costello, the director of the Alliance for Gambling Reform, said the investigation raised "serious questions about the culture and operation at Australia's biggest casino".

Late last year, whistleblowers from the casino accused Crown of instructing staff to remove betting options from poker machines.

After initially denying the button-blanking allegations, Crown told the stock exchange that it had removed betting options on 17 of its 2,628 machines over the three-week period for a trial.

A punter claims picks were used to jam buttons to allow illegal continuous play. ( ABC News: Margaret Burin )

In a statement, the regulator said the move had contravened gaming laws.

"The blanking plates concealed play line options so that only minimum and maximum betting options were available," it said.

"The commission considers that the way in which Crown used blanking plates in the trial constitutes a variation to the gaming machines and therefore required approval by the VCGLR, and that Crown's failure to obtain approval means it has contravened the Gambling Regulation Act 2003."

But it found the breach happened as part of a trial, and was not a deliberate move by casino management. Rather it was done "by a small group of Crown staff" who did not believe they needed approval to make the changes.

Casino management 'blaming anonymous staff': Costello

The Victorian Government is currently conducting its five-yearly review of Crown's licence.

Mr Costello questioned the accountability and culture of casino management.

"There have been so many governance issues involving Crown and its controlling shareholder since the last five-yearly review that the alliance now believes the Victorian Government should use this opportunity under the law to impose a new licence condition which requires James Packer to reduce his voting power over the Crown Melbourne licence to less than 20 per cent," Mr Costello said.

James Packer is Crown's biggest shareholder. ( AAP: Tracey Nearmy )

"In this situation where Crown has suffered the biggest fine in its 25-year history, you shouldn't just blame anonymous staff, but instead show some clear accountability amongst senior executives and the directors, most of whom have been personally selected by the controlling shareholder, James Packer."

In March, Mr Packer sold more that $100 million worth of his shares in Crown Resorts, which owns the Melbourne and Perth casinos.

He resigned as director soon after for mental health reasons.

He remains Crown's biggest shareholder with a 47 per cent stake worth more than $4 billion.

The commission found the trial did not affect the percentage of wagered money that was paid back to players.

"Crown acted quickly to cease the trial following a complaint and before the matter was raised with the VCGLR," it said.

Crown said it still maintained the trial did not require prior approval, but it respected the VCGLR's decision.

Minister for Gaming and Liquor Regulation Marlene Kairouz said breaching the regulations was "unacceptable".

"The independent commission has conducted their investigation, and appropriately, issued a significant penalty for this breach," she said.

Fine 'just small change' for Crown

Whistleblowers previously told the ABC they suspected the removal of buttons was aimed at increasing punter losses, by forcing them into making higher bets.

This week, a former patron produced a Crown-branded "pick" allegedly used to jam poker machine buttons in place, in what she said was more evidence of improper conduct at the casino.

Federal independent MP Andrew Wilkie handed that evidence, along with punter loyalty cards, to the VCGLR.

Crown believes it did not require prior permission to conduct the button trial. ( ABC News: Diana Hayward, file. )

The letter of censure requires Crown to draft an updated compliance framework within the next six months, and explain how the updated framework will prevent future breaches.

The regulator said it was the largest fine ever handed to Crown.

Charles Livingstone, who researches the social effects of gambling and gaming policy at Monash University, said the fine was not tough enough.

"A damp feather would be a fairly significant penalty in comparison to this fine in my opinion," he told ABC Radio Melbourne.

"I suppose the regulator thinks that by suggesting a $300,000 fine, that that will make people think that it's a big deal. It's not a big deal. That's just small change to these people."