The Standard asked financial firms about an audit covering a decade.

One experienced south-west accountant said a full audit over 10 years would be "almost impossible" to conduct.

"That's not how it works," he said, explaining audits were generally done on samples of records and depending on those results, often focused on areas of interest.

Another accountant said audit consultant fees would be up to $1 million and another said it would stretch into hundreds of thousands of dollars.

Another expert confirmed some well-known Melbourne-based auditors charged $700 per hour.

Warrnambool Ratepayer Association president Brian Kelson said he didn't know what the procedure would be if the state government put in an auditor.

"I know $1 million is a lot of money, but how much would it save?" he asked.

"I don't know if the council pays or the government.

"I would like to see the government pick up the tab.

"I still believe it's not just monetary value, it's a trust value."

Ratepayers Victoria urged the council to conduct the full audit.

President Dean Hurlston said the group wanted to see trust in the council restored.

"We believe the only way to restore public confidence in WCC is to address the issues, publish a full audit of the last 10 years of expenditure and tighten all controls without delay," he wrote in a letter to all councillors.

Warrnambool mayor Tony Herbert encouraged anyone who thought there was financial wrong-doings within the council to contact Victorian watchdog Independent Broad-based Anti-corruption Commission.

"If that's what people want they can go to these organisations and feel they will get support," Cr Herbert said.

"That's what they are there for.

"If council has done the wrong thing it will be found out during that process."

At Thursday's special meeting councillors voted to appoint an external auditor to look into its credit card spending, policies and procedures and misuse that was identified last year.