Metropolitan Police Commissioner Sir Ian Blair has called for celebrities caught snorting drugs on camera to be put on trial.
He said jurors should be given the chance to decide if suspects are taking illegal substances or not.
Prosecutors often do not charge those caught on camera because police cannot prove what substance they are taking. They fear defendants could successfully argue they were snorting talcum or baking powder and not cocaine.
In an interview with London's Evening Standard, Sir Ian said his officers had contacted the Crown Prosecution service (CPS) to discuss a change in policy.
He said: "The investigation of these cases is difficult due to there being no substance that can be forensically analysed and used for prosecution evidence. We are keen to explore whether there are further options that can be considered."
Supermodel Kate Moss was famously captured on a mobile phone video snorting white powder in a west London recording studio. And her former boyfriend Pete Doherty was filmed injecting drugs while singer Amy Winehouse was caught on camera smoking what appeared to be crack cocaine.
Referring to Moss, Sir Ian said it is "reasonable" for a jury to ask to be convinced the substances are legal. He said they might ask: "I can see that behaviour, you convince me that you're taking talcum powder because ... that's an unusual way to take it."
Sir Ian added: "My position is that a sensible jury would not expect people to be sniffing talcum powder."
Scotland Yard was reported to have spent £250,000 investigating the footage of Moss apparently snorting cocaine through a rolled-up £5 note. But prosecutors said there was not a realistic prospect of conviction because they could not prove what the substance was.
The decision came despite comments by Sir Ian at the time that any move to charge Moss would take into account her effect on impressionable young people. The CPS said the drug could also have been ecstasy or amphetamines, which attract different penalties for their use.
