Victorian regulators have slapped a $300,000 fine on Australia's biggest casino for tampering with its slot machines to limit betting options.

The Victorian Commission for Gambling and Liquor Regulation (VCGLR) determined that blanking plates were placed over certain buttons on 17 poker machines in March and April last year.  For this, Melbourne's Crown casino was given a $300,000 fine and a letter of censure.  But Crown management was exonerated, because the investigators determined the action was carried out by a small group of staff without approval of higher-ups.

"This is the largest fine the commission has issued to Crown and reflects the seriousness with which it considers the matter," the VCGLR said in a statement.

"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. 

"The contravention was not deliberate.  The decision to conduct the trial was made by a small group of Crown staff who did not believe approval was required and who failed to consult internally, or with the VCGLR, to check whether approval was required before commencing the trial."