Victoria's royal commission into the use of police informants has revealed that at least three other lawyers were approached by police to work with them, including one who has since been murdered.

Key points: The royal commission sparked by the Informer 3838 scandal opened in Melbourne this morning

The royal commission sparked by the Informer 3838 scandal opened in Melbourne this morning Lawyers, court clerks and a legal secretary were listed as police contacts or informers, the commission has revealed

Lawyers, court clerks and a legal secretary were listed as police contacts or informers, the commission has revealed Commissioner Margaret McMurdo said the accuracy of information provided by police would be investigated

In its first hearing, the Victorian Royal Commission into Management of Police Informants heard Victoria Police provided information three days ago, which included details of other legal professionals on police files.

They were:

A court clerk registered as police informer from January 8, 2015 until deregistered on May 11, 2016

A court clerk registered as police informer from January 8, 2015 until deregistered on May 11, 2016 A court clerk or legal secretary, who did not appear to be a practising lawyer, registered from October 1, 2009 until deregistered on May 11, 2016

A court clerk or legal secretary, who did not appear to be a practising lawyer, registered from October 1, 2009 until deregistered on May 11, 2016 A legal secretary in a corporation who was registered only as a community contact, from January 8, 2015 until May 11, 2015

A legal secretary in a corporation who was registered only as a community contact, from January 8, 2015 until May 11, 2015 A solicitor who police stated was registered only as a community contact from April 10, 2014 and deactivated on May 12, 2014

A solicitor who police stated was registered only as a community contact from April 10, 2014 and deactivated on May 12, 2014 A former solicitor who had significant health issues and was deemed unsuitable, so was never registered as a police informant

A former solicitor who had significant health issues and was deemed unsuitable, so was never registered as a police informant A self-proclaimed legal advisor but was not a registered legal practitioner, who police had a file on from December 4, 2015 to January 26, 2016

Commissioner Margaret McMurdo AC said there was an additional practising lawyer-turned-police-informant, who police refused to provide details on, because he was now the subject of a murder investigation.

She also said the accuracy of the information provided by police would be investigated, along with whether there were any further police informants with legal obligations of confidentiality or privilege.

The commission's terms of reference also allow it to investigate the use of other informers by police, referred to by the commission as "human sources".

Sorry, this video has expired Why you should care about the Lawyer X affair ( James Oaten )

Informer 3838 'will be cooperative'

The royal commission was set up by the Victorian Government last year to examine Victoria Police's use of a criminal defence lawyer who was simultaneously working as a police informer during Melbourne's bloody gangland war.

The informer has been referred to as Informer 3838, Lawyer X and EF in court documents and media reports.

Counsel assisting the commissioner, Chris Winneke QC, told the hearing Informer 3838 would cooperate fully with the probe.

"The commission is in communication with EF, via her legal representatives, and it's understood that she will be cooperative, assisting the commission in its investigation," he said.

Lawyer X represented a number of prominent gangland figures, including drug kingpin Tony Mokbel and Calabrian mafia boss Pasquale Barbaro.

"It's now come to light that EF was first registered as a human source by Victoria Police in 1995, then again in 1999," Mr Winneke said.

"It is known that EF represented many clients between her practice as a lawyer in 1996 and her deregistration as human source in 2009."

Tony Mokbel, who is serving a 30-year prison sentence for drug trafficking, could now challenge his convictions. ( AAP: Julian Smith )

The task of working out how many cases could be tainted due to the use of Informer 3838 will mean reviewing vast amounts of documents and police records but also "original voice recordings of discussions" between the former lawyer and her handlers, he said.

"These are materials that will be examined closely in order to determine what information was provided, whether it was provided in breach of duties and what use it was put to in ongoing investigations and prosecutions, " Mr Winneke said.

Victoria's Director of Public Prosecutions (DPP) wrote to more than 20 of Lawyer X's former clients, including a number of Mokbel associates, to let them know their convictions were potentially tainted by the legal scandal.

Chris Winneke QC told the hearing Informer 3838 would assist the commission. ( Supplied: Royal Commission )

High Court condemned 'reprehensible' arrangement

Court documents made public in December revealed Informer 3838 claimed to have helped police in as many as 386 cases during her time as an informer.

She provided information to police about her clients, including Pasquale Barbaro, who was convicted for importing Australia's largest importation of ecstasy, hidden in thousands of tomato tins.

The revelations opened up the prospect of criminals having their convictions overturned, allowing them to walk free from prison, and have potentially exposed the state to claims for compensation from those affected by the lawyer's work as an informer.

The High Court said Victoria Police's actions in using the informer were "reprehensible" and the lawyer had committed "fundamental and appalling breaches" of her obligations and the arrangement had debased fundamental premises of the criminal justice system".