She said the jury was “faced with a ridiculous sideshow of false allegations” about drug use which made focus on the actual criminal trial impossible.
Francesca Grillo, 35, and her sister, Elisabetta, 41, were each found not guilty of one count of defrauding Ms Lawson and her former husband, Charles Saatchi.
Ms Lawson, 53, admitted during the three-week trial that she had taken cocaine, after allegations of drug use arose as part of the defence case. But Scotland Yard said last night it would not be investigating unless new evidence comes to light.
In a statement, Ms Lawson said: “When false claims about habitual drug use were introduced, I did everything possible to ensure the CPS [Crown Prosecution Service] was aware of the sustained background campaign deliberately designed to destroy my reputation.”
During the trial she had accused multi-millionaire art dealer Mr Saatchi of threatening to “destroy” her. She said that, despite doing her civic duty, she was “maliciously vilified without the right to respond”.
The Italian sisters had been accused of using company credit cards, spending hundreds of thousands of pounds on designer goods for themselves while working as personal assistants to the couple. They claimed every purchase had been approved by their then-bosses.
The trial could have collapsed after David Cameron, the prime minister, declared his support for “Team Nigella” in an interview halfway through the trial — his comments prompting the defence to call for the trial to be halted.
After a day of drama and tension at Isleworth Crown Court in west London, during which Elisabetta collapsed upon arrival, the younger sister was delighted to learn of the not-guilty verdicts. Neither woman had been in Court 8 when the jury foreman read out the verdicts. The pair had been excused from the dock because Elisabetta stopped breathing following a panic attack on Thursday and spent two hours in hospital.
Karina Arden, Francesca’s barrister, was seen in the court foyer after the verdicts, proclaiming to her client: “C’e un Dio!” — Italian for “There is a God”. Francesca replied: “C’e un Dio!” and the pair embraced.
Anthony Metzer, representing Elisabetta, said his client was “relieved”.
During the trial the jury heard details of an email sent by Mr Saatchi in which he accused Ms Lawson of being off her head on drugs and branding her “Higella”.
Ms Lawson admitted that she took cocaine with her late husband, John Diamond, when he found out he had terminal cancer, and on another occasion in Jul 2010 during her troubled marriage to Mr Saatchi.
The TV cook — who also admitted to smoking cannabis — told the court that the idea she is a “drug addict or habitual user of cocaine is absolutely ridiculous”.