But later, Commander Stephen Watson, of the Metropolitan Police, told the Sunday Telegraph that officers would examine the "implications" of what she had said under oath and seek advice on what to do next from the Crown Prosecution Service.
Read full coverage of the Nigella case here.
Police will consider whether to bring drug possession charges and could also interview her to attempt to identify her suppliers. Social services could also intervene either at the request of police or on their own initiative after claims that she used drugs in front of her children.
The developments came amid mounting anger from Lawson and her supporters over what they see as a determined campaign to smear her and damage her career after the collapse of her marriage to art dealer Charles Saatchi.
Friends said at the weekend that Lawson was furious about how allegations of her drug use had emerged. However, her supporters also made clear that she was pressing ahead with her work. Saatchi was understood to have left the country for a holiday in the Caribbean.
Lawson's spokesman disclosed that all her nine cookery books would be republished over the coming months with new cover designs. A new television series called The Taste - in which she stars as a cooking competition judge - is to be shown for the first time in a prime-time slot next month. The disclosure is an apparent sign of the cook's confidence that her career is unharmed by the court case.
But she faces a new investigation which could be protracted. Mr Watson, one of Scotland Yard's most senior officers, said officers would look at all aspects of what was said during the trial.
On Friday, Scotland Yard said: "At this stage the Metropolitan Police will not be investigating these allegations."
But Mr Watson said: "Frankly, I don't think the full colour of the Metropolitan Police Service's position was conveyed in that statement."
Scotland Yard's new review is likely to focus on evidence Lawson gave at Isleworth Crown Court on December 4. The cook disclosed that she took the Class A drug with John Diamond, her first husband, when he found out that he had terminal cancer. She also admitted smoking cannabis in the last year of her marriage to Saatchi.
She claimed in her evidence that Saatchi had "told everyone" he was taking cocaine out of her nose after he was photographed holding her neck at Scott's restaurant. She said the incident was provoked by another, unrelated comment.
Potential areas for the police to pursue include not just whether Lawson should be charged, but whether she can identify the suppliers of the cocaine.
However, legal experts and police officers said pursuing a case against her presented several difficulties.
Professor David Nutt, the former government adviser on drugs laws, said: "The law in this country is based on possession of drugs, not on their use. The police would not be able to prove it."
One former senior police officer said: "Clearly she was getting her drugs from someone and that, surely, must be a matter of public interest."
