The TV chef tells a court her ex-husband spread false allegations of drug abuse in an attempt to "destroy her reputation".
Nigella Lawson has told a court her ex-husband threatened to "destroy her" if she did not go back to him and clear his name.
The 53-year-old made the remarks when questioned about Charles Saatchi as she gave evidence at Isleworth Crown Court at the trial of two former personal assistants accused of spending thousands of pounds on company credit cards.
She said: "I have been put on trial here where I am called to answer, and glad to answer the allegations, and the world's press, and it comes after a long summer of bullying and abuse.
"He had said to me if I didn't get back to him and clear his name he would destroy me."
She said following a much-publicised incident at Scott's restaurant in Mayfair, London, where her ex-husband was pictured with his hand on her throat, false allegations of drug abuse about her began circulating on a "PR blog".
She added these allegations were "dedicated to salvaging Mr Saatchi's reputation and destroying mine".
The court heard she had been reluctant to give evidence at the trial and said Mr Saatchi made the comment in reaction to that reluctance.
Ms Lawson told the court that Mr Saatchi had a temper and "didn't like to take part in family life".
It is alleged that between January 1, 2008, and December 31, 2012, Italian sisters Elisabetta and Francesca Grillo committed fraud by abusing their positions while working for the couple.
The jury was told they are accused of using credit cards loaned to them by the TV chef and art dealer to spend more than £685,000 on themselves.
Ms Lawson told the court: "It's very difficult when you find out that someone you have loved and trusted could behave that way.
"In my heart of hearts I do not believe Lisa (Elisabetta) to be a bad person. I believe her not to have a very strong moral compass.
She added that she once took out £7,000 from her savings to pay for Elisabetta Grillo to have her teeth fixed.
Elisabetta, 41, sometimes referred to in court as Lisa, and co-defendant Francesca, 35, both of Kensington Gardens Square, Bayswater, west London, deny the charge against them.