The Met Police has been criticised by a watchdog for waiting three years to act on a damning review of its probe into a Westminster paedophile ring.
Operation Midland – sparked by false claims made by Carl Beech – cost £2.5m but led to no arrests.
The latest report comes after the home secretary ordered an inquiry last year into how the Met handled the criticism.
Inspectors said they were “pretty underwhelmed” by the force’s response to a critical review published in 2016.
Last year, Beech was jailed for 18 years for inventing false allegations of murder and child sexual abuse by high-profile figures, which led to Operation Midland.
Ex-High Court judge Sir Richard Henriques’ 2016 report said that 43 police errors were made during the investigation.
In a report published on Friday, the Inspectorate of Constabulary – the police watchdog – found the force’s bosses were concerned with “restricting access” to the 2016 report, rather than “learning the lessons from it”.
HM Inspector of Constabulary Matt Parr said: “We were pretty underwhelmed by the Met’s response for the first three years.
“It’s pretty clear generally learning lessons from the Henriques report doesn’t seem to have been the top priority and it should have been.
“There are claims that they intervened and they changed the training and produced new material, but when we actually started scratching the surface and saying, ‘who’s had it, what difference did it make,’ we really struggled to find any evidence.”
The report found that the Met had not done enough to learn lessons in 2016 and had only started acting on some of the recommendations towards the end of last year.
Former Conservative MP Harvey Proctor, who was falsely accused of murder by Beech, described the review as a “devastating criticism” of the Met.
He added: “It looks as though the Met only started to do things once they knew the inspectorate had been commissioned by the home secretary to report on it.”
In response to the report’s findings, the Met said the force had been “deliberately cautious” due to criminal proceedings and another investigation by the Independent Office of Police Conduct.
The Henriques report had reprimanded the force for believing Beech for too long, and was critical of a senior detective for announcing publicly that Beech’s claims were “credible and true”.
The latest review said there was a “fine balance” between the need to take victims seriously and the need for “thorough, impartial investigations”, but it was “critically important to guard against regression” given the police’s track record on crime recording.
It recommended changing guidance for police officers on the “concept of belief” of a victim, to make clear that once a crime has been recorded “any investigation should be conducted impartially to establish the truth”.
Harriet Wistrich, director of the Centre for Women’s Justice, hit out at these proposals, describing the recommendations as “most disturbing”.
She said: “Essentially, because one man made a series of allegations against high-profile individuals which were believed by police officers, all rape victims are to face further hurdles in the process to hold rapists to account.”