"If you want to put me on trial, put me on trial," Lawson said as she testified for a second day at the fraud trial of her two ex-employees. "I don't feel it is right to have me here as a witness for the Crown and treat me like this."
On Wednesday, Lawson acknowledged taking cocaine a handful of times but denied being a regular drug user. She was pressed on the subject again Thursday under cross-examination by a defense lawyer, who asked whether she had kept cocaine in a hollowed-out book containing jewelry including her late first husband's wedding ring.
Lawson denied it.
"If I was taking cocaine and cannabis to the extent you say, I wouldn't be standing here," she said.
"If you think I'm going to sabotage my health and leave my children as orphans, you are very wrong," said Lawson, who has a son and a daughter from her marriage to John Diamond, who died of cancer in 2001.
"I promise you ... regular cocaine users do not look like this," added the cook, known for her voluptuous figure. "They are scrawny and look unhealthy."
Elisabetta and Francesca Grillo, sisters from Italy, are charged with using credit cards loaned to them by Lawson and her ex-husband Charles Saatchi to spend 685,000 pounds (more than $1 million) on luxury clothes, accessories and rooms at high-end hotels. They deny the fraud charges.
The case has been overshadowed by revelations about the troubled relationship between Lawson and Saatchi, a wealthy art collector. The couple divorced in July after Saatchi was photographed grabbing Lawson's throat outside a London restaurant.
Lawyers for the Grillos allege that Lawson sanctioned their high spending in exchange for their silence about her drug use. They have quoted an email in which Saatchi accused Lawson of being "so off her head" on drugs she allowed them to "spend whatever they liked."
Lawson said that claim was "ridiculous." She denied misleading police by not mentioning earlier that she had occasionally taken drugs.
She said she was not proud of her past drug use but came clean to avoid being "bullied by lies" from Saatchi.
Lawson said "I would rather be honest and ashamed" than let false allegations stand.
"I'm not proud of the fact I have taken drugs but that does not make me a drug addict or a habitual drug user," she said.
The trial has generated huge media interest. Lawson, 53, entered the court on Thursday walking past dozens of photographers and television cameras.
Cross-examined by Francesca Grillo's lawyer, Karina Arden, Lawson denied using her court appearance to explain herself to the world's press or to hit back at her ex.
"I prefer to keep my private life private," she said. "I felt it was my duty to come."
Lawson spent two days in the witness box at London's Isleworth Crown Court, at times sparring with defense lawyers who quizzed her on details of her domestic life with Saatchi. Judge Robin Johnson several times asked attorneys to halt lines of questioning.
At other times, the evidence was leavened by flashes of wit.
At one point Arden told Lawson that she shared her "penchant for things Italian," and said she did not mean that as a criticism.
"I don't see how that could ever be interpreted by anyone as a criticism," Lawson replied.