The police watchdog acted after a series of scandals, including the murder of Sarah Everard by a serving officer and failures in the investigation into the serial killer Stephen Portthat it said were likely to have a “chilling effect” on public confidence.
Her Majesty’s Inspectorate of Constabulary also unearthed “systemic failings” in routine policing, such as the failure to record the reason for a quarter of stop-and-search operations and the failure to log 69,000 crimes a year.
A source close to Home Secretary Priti Patel accused Mr Khan of being “asleep at the wheel”.
But the Mayor hit back, saying he had been calling for some time for systemic and cultural changes in the force “in the face of opposition from Priti Patel and Boris Johnson”.
The HMI report was said to contain no direct criticism of Mr Khan — who as police and crime commissioner has overseen the Met for the past six years — or of the Mayor’s Office for Policing and Crime, which sets the Met’s strategy and its £4.6 billion annual budget.
But critics questioned the Mayor’s role and that of his deputy mayor for policing, Sophie Linden, who was asked at a public meeting on Tuesday night how the Met’s failings were not her responsibility or that of Mr Khan.
Nickie Aiken, the prominent London Tory MP, said: “Sadiq Khan cannot continue to pass the buck and blame others. Crime continues to climb on his watch, neighbourhood policing has been decimated. Perhaps it’s not the commissioner who needs changing but his deputy mayor for policing.”
Latest data from Mopac reveals that, in the 12 months to May, the total number of offences reported to the Met was up more than 10 per cent year on year to 850,162.
This included an 8.5 per cent rise in violence against the person — almost 250,000 crimes — sexual offences up 26 per cent, rape up 17 per cent and knife crime up five per cent, though homicide was down 10 per cent and youth homicide down a third.
The source close to Ms Patel said: “The Mayor’s focus on ideas not within his gift, like decriminalising drugs, means the force is now in special measures. He needs to get a grip instead of drifting through his time at City Hall.”
Speaking at the State of London debate last night, Mr Khan “welcomed” the decision of HMI to place the Met in special measures. He had previously referred the Stephen Port case to the inspectorate and has ordered a new strategy on the way the Met tackles violence against women and girls, in light of the murders of sisters Bibaa Henry and Nicole Smallman and of Sabina Nessa.
He said the next Met commissioner — either Sir Mark Rowley or Nick Ephgrave is expected to be appointed next month — needed to be a “reforming commissioner” to win back the trust and confidence of Londoners.
Ms Linden admitted that special measures “immediately won’t make a huge difference” to day-to-day policing. She said it would be up to the next commissioner to restore confidence but added: “It’s not just one person who can fix the Met.”
Susan Hall, leader of the GLA Conservatives, said: “Khan should be embarrassed with the decision to put the Met into special measures, but instead he has welcomed it in order to deflect any blame that sits with him.
“This damning indictment is a sign of his total failure to deliver for Londoners. Rather than take responsibility and take tough decisions, he has left the problems at the feet of the new incoming commissioner.”
Today 29 London Labour MPs signed a letter organised by Dawn Butler, the MP for Brent Central, saying they had been calling for several years for changes to the Met to be made in the public interest but had been met with resistance.
Sir Hugh Orde, a former deputy assistant commissioner at the Met, said it would be unable to make progress while a “political bun fight” was in progress.
He told LBC: “There is a real issue of leadership clearly evident in the Met. I think this goes back a long way, some of this started way beyond the last commissioner.
“My personal view is the Met has got too big and it almost needs to be broken down into five areas like it was before with real grip and real care and effort at working with communities.”
A source close to Mr Khan said on Wednesday: “The Home Secretary oversees policing in England and a significant number of the forces she oversees are now in special measures. That fact tells you all you need to know about policing under this Tory government.”
A spokesman for HMI inspectorate declined to comment.