TV presenter Nigella Lawson will face no further action by police over her admission that she used drugs.
During her testimony at a fraud trial involving her personal assistants, she admitted taking cocaine in the past but denied being an addict.
The Met said a team had investigated the evidence and decided a prosecution would not be in the public interest.
It said any action could deter witnesses from giving evidence in future trials.
Sisters Francesca and Elisabetta Grillo, of Bayswater, west London, were cleared of defrauding Ms Lawson and her former husband Charles Saatchi.
At their trial, Ms Lawson said she took cocaine with her first husband John Diamond when he found out he had terminal cancer, and in July 2010 in the later years of her marriage to Mr Saatchi.
She also admitted cannabis use in the last year of her marriage to the businessman and art dealer.
In an email read out at Isleworth Crown Court , Mr Saatchi claimed Ms Lawson's drug use meant she allowed their former assistants to spend what they liked.
Police announced in December that a specialist team would examine the evidence as part of a review into the case.
That review has now concluded and in a statement, the Met said any police action had to be "proportionate".
"There are serious public interest concerns about the message any prosecution would send out to potential witnesses and victims in the future," it said.
"Whilst witnesses clearly cannot simply admit to any offence under oath without consequences, this has to be balanced with the requirement for victims and witnesses to tell the truth.
"Further police activity may deter victims from being candid with police and in court for fear of future investigation."
Ms Lawson previously said she was "disturbed" by the court process.
A spokesman for the celebrity said she would not be commenting on the police's decision.