The IRA spy who was known as Stakeknife died several days ago and was buried last week.
The British army agent was widely named previously as Freddie Scappaticci, who had always strongly denied the allegation.
The West Belfast man would have been in his 70s and had left Northern Ireland around 2003.
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This is when he was first accused of being the highest-ranking British spy in the Provisional IRA’s ranks.
Stakeknife worked within the IRA’s notorious “nutting squad” interrogating suspected informers during the Troubles.
The alleged activities of Stakeknife are under investigation in Operation Kenova led by former Bedfordshire chief constable, Jon Boutcher.
The report from the probe into crimes such as murder and torture linked to Stakeknife, and the role played by the security services, including MI5, was due to be published in early 2023.
Mr Boutcher said his team was made aware last week of the passing of Mr Scappaticci.
He said his staff are working through the implications of Mr Scappaticci’s death and will publish an interim report this year.
Mr Boutcher said: “We remain committed to providing families with the truth of what happened to their loved ones and continue to actively pursue criminal charges against several individuals.
“We will publish an interim report on [Operation]Kenova’s findings this year.
“We also recognise that people may now feel more able to talk to the Kenova team following the death of Mr Scappaticci, who had long been accused by many of being involved in the kidnap, murder and torture of potential PIRA informants during The Troubles.
“I appeal to anyone with information that might help those impacted by the events we are investigating to contact us in confidence to help families understand what happened during these difficult times.” Belfast’s KRW Law last night said
the news would “frustrate” many families who had been waiting for the report.
The firm is representing relatives of some of those killed by the IRA’s internal security unit, the “nutting squad”.
It said news of the death would have an impact on the publication of the report.
The firm added: “Families of victims will rightly ask questions. Their cynicism is heightened upon learning that news of Scappaticci’s burial seems to have been kept quiet by the authorities over the Easter weekend.
“People just aren’t happy and that’s only to be expected given the unexpected news.
“Answers will be needed sooner rather than later given heightened expectations that after all these years they would finally get some degree of closure.”
The law firm also said there was a “significant” amount of litigation linked to Mr Scappaticci, including “over 35 high court civil actions alleging collusion against him and State agencies together with judicial review challenges touching upon his status as a protected State intelligence asset”.
They added: “We have seen it before so many times previously with agents and informants dying before legal processes played out and robbing victims of some semblance of justice.
“Unfortunately we may now be seeing that again.”
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