By Nigella Lawson and Charles Saatchi's former aides Francesca and Elisabetta Grillo have been found not guilty of fraud.
During the trial at Isleworth crown court in west London, Lawson admitted to infrequently using cocaine and cannabis, but denied being a habitual drug user.
Saatchi was accused of being a bully who threatened to "destroy" his ex-wife.
Elisabetta 41, and her sister Francesca, 36, had been accused of fraudulently spending £685,000 between 2008 and 2012 on credit cards and taxi accounts without authorisation.
The sisters were allowed to hear the verdict in an adjacent room, as Elisabetta had suffered several panic attacks during the trial.
"My God, I am just shaking," said Francesca. "We can go home."
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Her barrister Karina Arden added: "We're delighted with the result."
As part of their defence, the Grillo sisters claimed that Lawson allowed them to use the credit cards on the understanding that they would keep her drug use secret.
Saatchi sent Lawson an email, later read out in court, claiming that "the Grillos will get off on the basis that you and Mimi [her daughter] were would keep her drug use secret that you allowed the sisters to spend whatever they liked".
However, Saatchi later admitted in court that he had never seen Lawson taking drugs and did not know if she ever had done.
In a magazine interview conducted during the trial, Prime Minister David Cameron was asked if he was "Team Nigella" and replied: "I am. I'm a massive fan."
He continued: "[My daughter] Nancy and I sometimes watch a bit of Nigella on telly. Not in court, I hasten to add."
Judge Robin Johnson told the jury to disregard the remarks, adding: "It is of regret when people in public office comment about a person who is involved in a trial which is in progress."
It has now emerged that Cameron's "unprecedented" comments were considered an "abuse of process" that may have threatened the case.
