The guidance, issued in the wake of former officer's Wayne Couzens' sentencing for murder, sparked a furious response from campaigners who say the advice effectively means people being told they must protect themselves from the police.
Couzens was given a whole life sentence for the rape and murder of Sarah Everard, who he kidnapped after carrying out a false arrest while still a serving police officer.
In response, the Met Police said women stopped by lone officers could ask where colleagues are, where they have come from, why they are there, and exactly why they are stopping or talking to them
If still concerned, people are being advised to shout out to a passer-by, run into a house, knock on a door, wave a bus down, or call 999.
But critics have said there is nothing Ms Everard could have done to avoid being abducted by Couzens as she walked home from a friend's house.
Prime Minister Johnson insisted that police are "overwhelmingly trustworthy" but said if people are concerned they should "seek help" in the way advised.
Asked about the Met Police advice, the PM told the BBC: "If you are suspicious about the way in which you are being treated by a police officer and you are worried for some reason, then clearly you should seek help in the way you have described.
"My view is that the police do - overwhelmingly - a wonderful job and what I want is the public, and women in particular, girls and young women, women of all ages, to trust the police.
"They are overwhelmingly trustworthy."
The Met announced it will no longer deploy plain clothes officers on their own after the sentencing hearing was told Couzens had used lockdown rules to falsely arrest Ms Everard during the abduction.
The force has also promised to publish a new strategy for tackling violence against women and girls, outlining how it will prioritise action against sexual and violent predatory offenders.
The prime minister said various investigations into matters related to Couzens by the Met Police and the Independent Office for Police Conduct should be allowed to proceed, as he rejected calls for an immediate public inquiry.
He told the BBC: "We do need to look systemically at not just the Wayne Couzens case but the whole handling of rape, domestic violence, sexual violence and female complaints about harassment all together."
Asked about cuts to budgets, Mr Johnson said "record sums" were being put in to "all parts of government" but the problems in the justice system were about more than money.
"The delays are coming up in that moment between the report of an offence and the passing of that offence to the prosecutors.
"What is not working properly is that the CPS and the prosecutors are not working well enough with the police to assure women that a decent case is presented and that there is a chance of prosecution."