A former police officer has admitted using gangland lawyer Nicola Gobbo as a police source was risky, but says the deaths of dozens of underworld figures in the 2000s left the force in a desperate situation.

Key points: A former senior police officer says there were ethical questions raised about using informer Nicola Gobbo

A former senior police officer says there were ethical questions raised about using informer Nicola Gobbo The commission hears Ms Gobbo provided information about Tony Mokbel offering police a $2 million bribe

The commission hears Ms Gobbo provided information about Tony Mokbel offering police a $2 million bribe A second officer tells the hearing the police protecting slayed informer Terence Hodson and his wife Christine were incompetent

Terry Purton was a senior member of Victoria Police during the gangland war and knew Ms Gobbo was providing information that could incriminate her clients.

Ms Gobbo was revealed as the informant at the centre of a 15-year Victorian legal scandal that sparked the royal commission into the police use of informants.

Mr Purton told the royal commission the risks associated with using Ms Gobbo's information were outweighed by the need to protect the public.

"In the situation we are talking about here, where 25 people have been slaughtered on the streets of Victoria, you've got to say, do we try and stop all these killings and not use someone as a source, or do we allow the carnage to continue?" Mr Purton said.

"It was a terribly dangerous time; the streets were awash with blood and sometimes these were occurring on a daily basis and we were desperate to stem the flow of murders and protect the community."

Mr Purton said while there were ethical questions about getting information from Ms Gobbo, Victoria Police did not act illegally.

"My view is it's not a criminal offence to engage a barrister as an informer," Mr Purton said.

'Mokbel wants to bribe someone'

Earlier in his evidence, Mr Purton said in 2005 drug boss Tony Mokbel offered a police officer $2 million to remove a tape recording that might incriminate him.

He wrote about the offer in his diary at the time.

"Tony Mokbel wants to bribe someone to produce tapes and see if he can be removed from [Operation] Quills," Mr Purton wrote.

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When questioned by counsel assisting Andrew Woods, Mr Purton confirmed the person who provided that information about Mokbel wanting to bribe someone was Ms Gobbo.

Ms Gobbo was Mokbel's lawyer at that time.

It was unclear who the police officer was and if the bribe was accepted.

'Incompetency' factor in informer murder

Another former police officer, Charlie Bezzina, told the commission police incompetency contributed to the murders of police informer Terence Hodson and his wife Christine.

The pair were shot dead in their Kew home in May 2004, not long after Mr Hodson agreed to give evidence about alleged police corruption.

Mr Bezzina, a former homicide detective, led the investigation into the Hodson murders.

He told the commission he was annoyed the ethical standards department, who were managing Mr Hodson, left him vulnerable to attack.

Mr Bezzina said Mr Hodson had not wanted to go into witness protection.

"Why did they leave Hodson to his own devices?... They allowed him to set up his own video surveillance," he said.

"Why didn't [police] set up your own surveillance unbeknownst to Hodson?

"That was a big issue for me. That to me was incompetent."

Christine and Terence Hodson were shot dead in their home.

Mr Bezzina also took issue with the role played by former chief commissioner Simon Overland.

Mr Overland was an assistant commissioner at the time of the Hodson murders and oversaw a series of investigations into the deaths.

"I formed a view down the track that Overland was running his own investigation behind my back while I'm leading the investigation," Mr Bezzina said.

In 2009 former drug squad detective Paul Dale was charged with the Hodson murders, but the charges were later dropped when underworld boss Carl Williams was killed in prison.

Mr Dale is expected to give evidence at the royal commission in the next fortnight.

Mr Overland is expected to be called as a witness later this year.