A court clerk, two legal secretaries, a solicitor, a former solicitor, a “self-proclaimed legal adviser” and a lawyer who has since died all acted as police informants or community sources while police fought to prevent the identification of the Melbourne gangland source Lawyer X, a royal commission has heard.

Commissioner Margaret McMurdo described the positions of the six informants in a bid to combat “misinformation” about their identities, which have been the subject of intense gossip and speculation in legal fraternities and the media since Victoria police revealed that Lawyer X was not the only legal source on their books.

In the first directions hearing to the royal commission into the use of police informants in Melbourne on Friday, McMurdo said a letter from Victoria police, dated 2014 but only recently provided to the commission, said that “another lawyer, now deceased, had previously provided information to Victoria police”.

That lawyer has been identified in some media reports as murdered mafia lawyer Joe Acquaro.

The other six informants include a court clerk, who was registered as a police informer from January 2015 to May 2016, when they were deemed “unreliable and too ‘risky’ to be used”.

The other informants were a court clerk or legal secretary who “did not appear to be … a practising lawyer”, registered from October 2009 to May 2016; a legal secretary who was registered as a community contact from January to May 2015; a solicitor registered as a community contact from April to May 2014 and did not inform on their own clients; a former solicitor who was considered and dismissed for use as an informant for three days in February 2015; and a “self-proclaimed legal adviser” who was registered for just over a month from December 2016 to January 2016.

The royal commission was called in December following the publication of a unanimous high court decision ordering that former clients of a person known variously as Lawyer X, Informer 3838, or EF be told that they were acting as a police informant.

Lawyer X’s identity is still suppressed.

The high court’s decision followed years of attempts by both the lawyer and Victoria police to block the release of the information, which they said would put the life of the lawyer and their family at risk.

McMurdo said that the use of a lawyer as a police informant was a breach of fundamental principles of the legal system.

“The police use of lawyers to inform on their clients has obvious potential to undermine the criminal justice system and the public’s confidence in it,” she said.

If that happened, she said, “the criminal justice system would regress into a dysfunctional, far more costly, clogged quagmire of universal distrust.”

It could undermine past convictions. In Lawyer X’s case the convictions of 22 people, including gangland figure Tony Mokbel, could be impacted.

“The whole costly, clandestine and unlawful exercise cannot legitimately achieve its original goal,” McMurdo said. “All it achieves is to undermine the very criminal justice system legal practitioners and police officers are duty bound to uphold and serve.”

Chris Winneke QC, counsel assisting the commissioner, said that ignoring obligations of legal privilege could “see guilty offenders walk free”.

Winnike said Lawyer X was expected to “cooperatively assist the commission with its investigation” and that it was “expected that all relevant witnesses will be examined, whether voluntarily, or by compulsion”.

He said the commission would examine recordings of Lawyer X talking to their police handler, as well as diaries recording those interactions. Documents have been sought from 40 other individuals and entities.

Public hearings are expected to begin late March and the commission is due to report on 1 July about cases specifically relating to Lawyer X.

McMurdo is conducting the commission alone after her co-commissioner, former South Australian police commissioner Malcolm Hyde, declared a conflict of interest and resigned.