After a recent court case raised allegations of extensive drug use, will celebrity chef Nigella Lawson face an investigation? Nigella Lawson's former personal assistant has told a court that she frequently found evidence of drug use. Nigella Lawson faces the attention of police if evidence emerges of her alleged drug abuse. NIGELLA Lawson could face a drugs investigation if "new evidence" emerges, Scotland Yard says. At this stage officers have no plans to probe allegations the celebrity cook took cocaine - but a spokesman for the Metropolitan Police said detectives will review this decision should proof come to light. The Met's statement will cast a shadow over Miss Lawson's attempts to launch a career in the United States, which has a zero tolerance stance on drugs. Yard sources said officers need 'physical evidence' of Class A drug use before launching an investigation. But critics claimed Miss Lawson's admission that she had used cocaine, made during the fraud trial of her former housekeepers, was sufficient grounds for a probe. A leading drugs campaigner called on the Met to begin an immediate investigation into Miss Lawson, claiming she has received preferential treatment because she is a celebrity. A Met spokesman said: "Allegations that one of the (alleged) victims was involved in taking Class A drugs have been made during the course of this trial. At this stage the Metropolitan Police will not be investigating these allegations. Elisabetta Grillo, centre, and Francesca Grillo (head down, to right) leave Isleworth Crown Court. The Italian sisters, who worked as assistants to Nigella Lawson and Charles Saatchi, were found not guilty of defrauding their former employers. Should any evidence, and that includes material from the trial, that could be investigated come to light this decision will be reviewed. During the trial of Lisa and Francesca Grillo, the jury was told of an email in which Miss Lawson's former husband, Charles Saatchi, claimed her drug use meant she allowed the sisters to spend what they liked. In the message, in which he referred to her as "Higella," he said: "Of course now the Grillos will get off on the basis that you ... were so off your heads on drugs that you allowed the sisters to spend whatever they liked and, yes, I believe every word the Grillos have said, who after all only stole money." Giving evidence, Miss Lawson said: "I have never been a drug addict. I've never been a habitual user. There are two times in my life when I have used cocaine. The first was when Mr Diamond found out his cancer was terminal, and she took it with him on six occasions. The second, she claimed, was in July 2010 when she alleged she was being "subjected to intimate terrorism by Mr Saatchi." But defence lawyers urged jurors to treat the TV cook's evidence about limited drug use with caution. In his closing speech Anthony Metzer QC, defending Lisa Grillo, told jurors Miss Lawson had "rehearsed" her evidence about her limited drug use. Court Sketch of Nigella Lawson giving her evidence. He said she was a "formidably intelligent" woman who was forced to admit some of the allegations made by the Grillos. The Met's reluctance to launch an investigation into Miss Lawson's cocaine use - and whoever supplied the drug to her - appears to be at odds with Yard boss Sir Bernard Hogan-Howe's previously tough stance on substance abuse. Earlier this year, he said millions of professionals should face mandatory drug testing at work. Anyone who failed a test and refused help to get clean should lose their job, he added in a speech in January to the all-party parliamentary group on cannabis and children. The Metropolitan Police Commissioner said that as well as "robust" policing of dealers, action was needed to discourage the demand for illegal substances. He said testing could take place in "all occupations" but cited in particular teachers, intensive care nurses and transport staff. One of Sir Bernard's predecessors, Sir Ian Blair, was equally determined to crack down on middle-class cocaine users. On his first day as Met chief in 2005, Sir Ian said the cocaine trade caused great misery and violence and those who considered it socially acceptable to use the drug, and created a demand for it, should realise it was not a "harm-free pleasure." Charles Saatchi is escorted by a court official as he arrives at Isleworth Crown Cour. But the following year, a cocaine probe into supermodel Kate Moss ended in farce. Questions about the Met's investigation came as Miss Moss was officially cleared of claims she took "line after line" of cocaine. The Crown Prosecution Service formally announced there was "insufficient evidence" to prosecute the model after she was pictured apparently snorting the banned substance at a recording studio. A senior prosecution lawyer said there was an "absolutely clear indication" she was using drugs and providing them to others. But because of a minor legal loophole, police could not prove which type of drug was involved and she could not be charged. The failure of the investigation in the face of the damning photographs, brought widespread condemnation from politicians and campaigners. Mary Brett, of the charity Cannabis Skunk Sense, said: "It appears Nigella Lawson is being treated differently by police because she is a celebrity. It sends out the message that if you are famous, there is a good chance you will get away with it ... I would urge [police] to launch an immediate investigation into Nigella Lawson's alleged drug taking. British television chef Nigella Lawson leaves Isleworth Crown Court in west London after giving evidence in the case in which her two personal assistants (Elisabetta and Francesca Grillo) were accused of defrauding her and former husband Charles Saatchi.