Metropolitan Police Commissioner Sir Ian Blair has said that celebrities who are pictured apparently taking drugs should be put on trial to prove they were snorting talcum powder and not cocaine.
Blair said he wanted juries to decide whether famous figures caught on film were indeed taking illegal drugs even if it was impossible for police to prove what the substance actually was.
But his comments, which came as a new report disclosed that Amy Winehouse and Kate Moss are seen as leading role models by many teenage girls, have been criticized by the country's top prosecutor, Sir Ken Macdonald.
Sir Ian wants the Crown Prosecution Service to look again at current rules which state that police cannot charge someone if they are unsure what substance they have been filmed taking.
Many public figures including Winehouse and Moss have escaped prosecution despite the publication of video footage, which appeared to show them taking drugs.
"My position is that a sensible jury would not expect people to be sniffing talcum powder," the Telegraph quoted Sir Ian, as saying.
"I expressed my concern over the Kate Moss stories, we did that investigation and we hit the same issue.
"At the moment the law says you must be in possession of a Class A or a Class B to be prosecuted. If you are seen on film then nobody can tell what the substance is.
"I think it is reasonable for a jury to say: 'you convince me that you are taking talcum powder' because it is an unusual way to take it," he added.
But Sir Ken, the Director of Public Prosecutions, accused Sir Ian of "completely misunderstanding" the law and said that he was "extremely surprised" that the Metropolitan Police commissioner wanted stars to face a jury if they are caught on camera apparently snorting cocaine or smoking crack.
He claimed the suggestion that the CPS does not pursue drug-taking celebrities is "completely untrue".
Sir Ken said: "I'm extremely surprised by comments attributed to Sir Ian Blair. If he is accurately quoted he appears to have completely misunderstood the law.
"The issue was not whether the white powder that Kate Moss was snorting was cocaine or talcum powder. The law required us to prove that it was either a class A drug or a class B drug. We could only base our case on one of these options.
"It was impossible for us to do this since cocaine - a class A drug - and amphetamine - a class B drug are both white powders."