David Carrick, 48, admitted responsibility to 49 offences over two decades after meeting several of his victims on dating websites.
He confesses to committing many rapes and sexual offences against 12 women while carrying a weapon and using his position to intimidate his victims.
The Met issued an apology after it became clear that between 2000 and 2021, he had been reported to the police in connection with nine incidents, including rape claims.
His misconduct was “unprecedented in policing,” according to a senior officer.
The Met’s assistant commissioner in charge of professionalism, Barbara Gray, said: “We should have spotted his pattern of abusive behaviour and because we didn’t, we missed opportunities to remove him from the organisation.
“We are truly sorry that being able to continue to use his role as a police officer may have prolonged the suffering of his victims.
“We know they felt unable to come forward sooner because he told them they would not be believed.”
When Carrick was detained in October 2021, he acknowledged to 24 counts of rape and was immediately suspended from service.
The Stevenage-born Carrick would dictate to the women what they wore, what they ate, where they slept, and even prevented some of the mothers from speaking to their own children.
When one woman did decide to report him, he was eventually stopped.
She contacted police in October 2021 as a result of coverage of sacked Metropolitan Police officer PC Wayne Couzens.
Through online dating services like Tinder and Badoo, Carrick, a member of the Parliamentary and Diplomatic Protection Command, met some of his victims.
He then exploited his position as a police officer to win their trust.
At Southwark Crown Court on Monday, he admitted to four counts of rape, false imprisonment, and indecent assault involving a 40-year-old woman in 2003.
In December, Carrick reportedly entered pleas of guilty to 43 charges, including 20 instances of rape.