People stopped by a lone plain-clothes officer should challenge their legitimacy, the Met Police says.
As it seeks to reassure women after the murder of Sarah Everard by a serving police officer, the Met said it was “entirely reasonable” to demand an officer’s identity and intentions.
Wayne Couzens showed a warrant card and used handcuffs as he kidnapped Ms Everard before her rape and murder.
The Met faces questions over whether chances were missed to stop him.
Couzens, 48, targeted Ms Everard, 33, on a street in south London in March. He has been sentenced to a whole-life prison term.
He had been linked to two previous allegations of indecent exposure.
Policing Minister Kit Malthouse said “officers up and down the land recognize the devastating consequences of this event”.
“There is a job to be done to rebuild trust by the police, particularly, I have to say, in London,” he told BBC Breakfast.
He said it was “reasonable” for a woman with doubts about a police officer’s conduct to make “lines of enquiry”, but that “won’t be appropriate in every circumstance” because officers “seeking to keep us all safe every day need to be able to go about their business”
Metropolitan Police Commissioner Dame Cressida Dick faces calls to resign over the force’s handling of the case, as Home Secretary Priti Patel said it raised “serious questions”.
Speaking outside the Old Bailey after Couzens was sentenced, Dame Cressida said “a precious bond of trust has been damaged” and she would ensure “any lessons” were learned.
As part of renewed efforts to ease fears in the capital, the Met will step-up “reassurance patrols” and treat indecent exposure allegations more seriously.
An extra 650 new officers will patrol busy public areas in London.
Scotland Yard admitted the case was part of a “much bigger and troubling picture”.
The force advised people detained by a lone plain-clothes officer to ask “where are your colleagues” and “where have you come from?”
It suggested other “very searching questions”, including “why are you here” and “exactly why are you stopping or talking to me?”
The force said that, to verify the answers, people should ask to speak to an operator on a police radio to determine if the officer is genuine and acting legitimately.
It added: “All officers will, of course, know about this case and will be expecting in an interaction like that – rare as it may be – that members of the public may be understandably concerned and more distrusting than they previously would have been, and should and will expect to be asked more questions.”
In the event someone believes they are in “real and imminent danger” the Met advised they “must seek assistance – shouting out to a passer-by, running into a house, knocking on a door, waving a bus down or if you are in the position to do so calling 999”.
It said it was unusual for lone plain-clothes officers to engage with people.
In the letter, the Met explained officers are expected to intervene when required, and even when off duty, and that they routinely carry warrant cards, and sometimes equipment when travelling.
Speaking to the London Assembly, Sir Stephen House, the Met’s deputy commissioner, said plain-clothes officers will not be deployed on their own and will be in pairs.
But he warned there would be occasions where that is not possible given that off-duty officers not in uniform “put themselves on duty” when they come across an incident.
Couzens, who had been a police officer since 2002, transferred to the Met in 2018 from the Civil Nuclear Constabulary, where he had worked since 2011. He passed vetting checks.
Assistant Met Commissioner Nick Ephgrave admitted a vetting check on Couzens was not done correctly when he joined the Met.
It meant a link to an incident of indecent exposure in Kent in 2015, involving a vehicle linked to Couzens, was missed.
Though AC Ephgrave said that even if it had come up in the vetting process, it would not have changed the outcome as Couzens was not named as a suspect.
Around 72 hours before Ms Everard’s abduction, Met Police officers received a separate allegation of indecent exposure which also identified the vehicle involved, registered to Couzens.
He was sacked by the Met in July after pleading guilty to Ms Everard’s murder.
Jess Phillips, Labour’s shadow minister for domestic violence and safeguarding, said there were gaps in the Met’s explanation of how Couzens passed its vetting checks and that trust in police was “very badly damaged”.
“We’ll be pushing ministers and the home secretary to have a look at what is going on in the vetting processes,” she said.
Another Labour MP, Harriet Harman, called for Dame Cressida to stand down, saying women’s trust in the force “will have been shattered”, while former Met chief superintendent Parm Sandhu also called for the commissioner to resign.
Cabinet minister George Eustice said the government had been working hard in recent weeks to devise a strategy to reduce violence against women and girls.
“We are looking at making our streets safer, designing out some of the risks, getting more CCTV, supporting more helplines,” he told BBC One’s Question Time.
“We’ve had a domestic abuse bill which has given new powers to the police to intervene earlier in a pro-active way and to protect witnesses from being intimidated by their abusers in court.”
Prime Minister Boris Johnson said on Thursday that people “must be able to walk on our streets without fear of harm and with full confidence that the police are there to keep them safe”.
“No woman should have to fear harassment or violence. We will do everything possible to prevent these abhorrent crimes and keep our communities safe,” he added.
Measures including a pilot scheme where plain-clothes officers patrol pubs and clubs were launched in England and Wales in the immediate aftermath of Ms Everard’s murder.
The Met said it would publish a new strategy for tackling violence against women and girls soon.