London's Metropolitan Police were placed under a special monitoring and improvement programme by a watchdog on Tuesday and told to develop an improvement plan after criticism of its handling of several high-profile cases.
Her Majesty’s Inspectorate of Constabulary said the force was being monitored through its Engage process, which "provides additional scrutiny and support to help it make improvements". The watchdog did not say what had triggered the move.
"A series of appalling scandals have not only exposed deep cultural problems but have damaged the confidence of Londoners in the capital’s police service," said Sadiq Khan, mayor of London.
"The decision by the HMIC to now move the Met into special measures has laid bare the substantial performance failings by the force."
The force was shaken last year by the abduction, rape and murder of Sarah Everard by one of its officers. Its policing of a vigil for the victim was later found to be unlawful by a London court.
The force has also been beset by revelations of a culture of bullying, racial discrimination and misogyny.
The Met said it recognised the cumulative effect of events and problems it faced.
"We are determined to be a police service Londoners can be proud of," it said in a statement. "We are talking to the Inspectorate about next steps."
In February, London police chief Cressida Dick resigned after Mr Khan had told her he was not satisfied she could root out the problems that existed within the force.
Her successor has yet to be appointed.
The watchdog says the Engage process is used when a force is not responding to a cause of concern, or is unsuccessful in addressing it.