"Numerous errors" were made in Scotland Yard's investigation into VIP paedophile allegations, an independent review has found.
Retired High Court judge Sir Richard Henriques said the decision to abandon the inquiry should have been taken much earlier.
He identified a catalogue of failings in the £2.5 million Operation Midland, which closed without a single arrest earlier this year.
Five officers have also been referred to police watchdog the Independent Police Complaints Commission over potential breaches in professional standards linked to Operation Midland.
In the report, the former judge said: "The principal cause of the many failures in this investigation was poor judgment and a failure to accurately evaluate known facts and to react to them.
"A major contributing factor was the culture that 'victims' must be believed."
The report states the main errors in the investigation were:
- To believe the complainant Nick was a credible person for too long;
- To say publicly that the allegations were credible and true;
- To obtain search warrants with flawed and incomplete information; and
- Not to have closed the investigation sooner.
The report suggests there could be a huge change in investigating sexual allegations and instruction to always believe a "victim's account" should cease.
It adds that complainants should not be called victims until the judicial process is finished.
Former Conservative MP Harvey Proctor, former Army chief Lord Bramall and late Tory peer Lord Brittan were publicly named in connection with the probe.
Commissioner Sir Bernard Hogan-Howe apologised to Mr Proctor, Lord Bramall and Lord Brittan for the "intrusion into their homes" and the impact of the investigation on their lives.
He said the public identification "compounded the harm of our investigative failures".
Mr Proctor had accused the Metropolitan Police of a "PR cover-up" for publishing findings from Sir Richard Henriques's examination of Midland on the day of the US election.
Metropolitan Police Commissioner, Sir Bernard Hogan-Howe said: "I accept on behalf of the Metropolitan Police accountability for these failures as I accept accountability for failures in any of our operations and investigations.
It is a matter of professional and personal dismay that the suspects in the investigation were pursued for so long when it could have been concluded much earlier."