The family of a private detective killed with an axe in a pub car park have accused the home secretary of "ignorance" and "unwarranted interference" after the publication of a report into his death was delayed.
Daniel Morgan’s family also claim the intervention is "inconsistent with the panel’s independence" and shows a "disturbing disregard for the public interest".
Mr Morgan was killed at the Golden Lion pub in Sydenham, southeast London, in March 1987.
Despite five police inquiries and an inquest, no one has ever been convicted of killing the father-of-two.
There are claims he was on the verge of exposing police corruption when he was attacked.
Corruption was a "debilitating factor" in the original investigation, Scotland Yard has admitted.
The review – set up by Theresa May in 2013 – is expected to have a sizeable chapter on officers’ alleged failings.
The panel examining the case had been due to publish its findings on Monday, but was informed by the Home Office that parliamentary time could not be found.
This week, the Home Office added that it wanted to review the document.
The Morgan family’s lawyer, Raju Bhatt, told the BBC his clients had "every reason to be suspicious about the motives behind this very belated and completely unwarranted intervention by the home secretary".
In a statement, the Daniel Morgan Independent Panel said it "believes that this last-minute requirement is unnecessary and is not consistent with the panel’s independence".
A Home Office spokeswoman explained the intervention by saying the home secretary had an obligation to make sure the report complied with human rights and national security considerations.
But the panel said it had already worked with lawyers and a special police team to ensure those concerns are met.
It also said the home secretary’s role was limited to reporting to parliament on the panel’s work, receiving the report, laying it before parliament, and responding to its findings.
Mr Morgan’s family said the delay in releasing the report was a "kick in the teeth".
In a statement, they added: "The home secretary’s intervention is not only unnecessary and inconsistent with the panel’s independence.
"It is an outrage which betrays her ignorance – and the ignorance of those advising her – with regard to her powers in law and the panel’s terms of reference.
"It also reveals a disturbing disregard for the public interest in safeguarding the independence of the panel and its report.
"For us as the family of Daniel Morgan, the home secretary’s belated and unwarranted interference in this process is simply unacceptable."
Mr Morgan’s brother Alastair tweeted: "We’re now looking to the Daniel Morgan Independent Panel to defend their independence and fend off this unwarranted intervention from the home secretary. We’re very hopeful that they will."
The Home Office spokeswoman added that the delay "has nothing to do with the independence of the report, and the Home Office is not seeking to make edits to it".
She added: "As soon as we receive the report, we can begin those checks and agree a publication date."