Victorian Premier John Brumby says Carl Williams was a serial killer and a royal commission into his death would be a waste of taxpayers' money.
Williams was bludgeoned to death inside Victoria's highest security prison on Monday.
Three separate inquiries have been launched into his death by the police - overseen by the Office of Police Integrity (OPI) - the coroner and Corrections Victoria.
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Mr Brumby said those probes were adequate.
'Waste of taxpayers' money'
"I know there's been some calls today for a royal commission, to be honest what occurred in the prison was obviously unacceptable, but the person concerned was a serial killer," Mr Brumby told reporters on Wednesday.
"I think it would be quite unnecessary and quite inappropriate use of taxpayers' money to have a royal commission.
"The three inquiries are there, I think they're more than enough to do the job."
Mr Brumby is also resisting renewed calls for an independent anti-corruption commission.
Such bodies in NSW and Queensland had turned into a "lawyers' picnic", he said.
"If I had the choice of putting tens of millions or hundreds of millions of dollars into an ICAC or putting it into hospitals, or bushfires, or more police, I'd choose the latter."
Mr Brumby said Victoria's prison system was the best in Australia in terms of recidivism rates.
