Charles Saatchi referred to his former wife Nigella Lawson as "Higella" and accused her of being so off her head on drugs that she allowed their assistants to spend money on whatever they liked, a court has heard.
Italian sisters Francesca and Elisabetta Grillo are due to go on trial accused of committing fraud while they worked as PAs to the celebrity couple.
Ahead of the case being heard at Isleworth Crown Court in west London, Judge Robin Johnson read out an email sent from Mr Saatchi to Ms Lawson following their high-profile divorce earlier this year.
In the email Mr Saatchi said: "Of course now the Grillos will get off on the basis that you ... were so off your head 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."
The millionaire art dealer called his ex-wife "Higella" in the email, which was sent on October 10, and signed off "Classy!", the court heard.
Judge Johnson said that when Mr Saatchi was asked by police to explain what he meant in the message to the TV chef, he said: "At the time of sending the email I was completely astounded by the scale of drug use set out in the statements (from the defendants).
"Nevertheless I did believe the allegations that I'm referring to in the email. I have been asked whether it referred to a belief that Nigella ... permitted the sisters to spend whatever they liked.
"I can't remember precisely what I had in mind. On reflection I was simply speculating that the sisters would use this information to defend themselves."
Judge Johnson said the allegations by Mr Saatchi were some of the many communications since the "unhappy events surrounding the witnesses' divorce this summer".
The pair broke up after pictures were published in a newspaper in June showing Saatchi holding his wife by the throat.
The incident on the terrace of Scott's restaurant in Mayfair, central London, was dismissed by Saatchi as nothing more than "a playful tiff" but he later accepted a police caution for assault.
Mr Saatchi went on to tell the Mail on Sunday that the pictures gave a "wholly different and incorrect implication".
Anthony Metzer QC, defending Elisabetta Grillo, told the court today that Saatchi had told lawyers he did not know about Lawson's alleged drug taking during their ten-year marriage and only found out as they were splitting up.
Referring to the incident outside Scott's, Mr Metzer said: "We are submitting the row that happened resulting in Mr Saatchi assaulting Nigella may have had something to do with Nigella taking drugs and may have something to do with the issue before this court of whether she gave them (the defendants) authority to use the cards."
Defence barristers acting for the two defendants had wanted details of the alleged drug use by Lawson to be heard in the case.
The judge concluded: "I will allow questions of Miss Lawson and witnesses as to the alleged taking of prescribed drugs or proscribed drugs."
Elisabetta, 41, and Francesca Grillo, 35, both of Kensington Gardens Square, Bayswater, west London, both deny the charge against them.
It is alleged that between January 1 2008 and December 31 2012, they committed fraud by abusing their positions as PAs by using a company credit card for personal gain.
Referring to the defendants, Mr Metzer added: "Our clients have been the innocent pawns in a rather unpleasant battle going on between Mr Saatchi, Miss Lawson and their lawyers. We come within the parameters of manipulation of the court."
The case was adjourned until 10.15am tomorrow and is expected to open at around midday.