One of Nigella Lawson's former aides alleged in court today that the celebrity chef "let the children smoke weed".
Elisabetta Grillo, 41, also told the court that Charles Saatchi only learned of his former wife's alleged drug habit on the day he was photographed with his hands around her throat at a restaurant.
She said it was this incident that persuaded her to include allegations of drug use by Ms Lawson in her defence case.
Miss Grillo and her sister Francesca are both accused of defrauding the couple by using a work credit card to buy luxury items, flights and hotel stays for themselves.
ITV News correspondent Dan Rivers reports:
Questioned by prosecutor Jane Carpenter to explain a duty-free transaction made in June 2010, Miss Grillo said: "It was cigarettes for the children. I bought them and Nigella allowed me to buy them.
"I don't remember how many packs. Nigella always told me to buy it."
Asked by Ms Carpenter: "What on earth did you think you were doing, buying cigarettes for under age children?"
Grillo said: "Well, if Nigella Lawson let the children smoke weed," before trailing off.
The former aide previously told the court that she had seen evidence of regular drug use at the home Nigella shared with her late husband John Diamond.
Asked if she had ever seen Mr Lawson actually taking drugs, Miss Grillo replied: "No".
Today, she admitted she had not initially wanted claims of drug use to be included in her defence case statement as she felt a "remnant of sympathy towards Ms Lawson".
"I didn't want to use it before because I wanted to protect her," she told the court.
But she said the incident at a Mayfair restaurant in which Mr Saatchi was photographed with his hands around Ms Lawson's throat made her change her mind.
I think especially when Charles picked her nose, it was the proof she still took drugs and he discovered that day. So we then decided it was the moment for everybody to know the truth - she could lie easily.
Miss Grillo's barrister Anthony Metzer QC read to the court a later additional statement that included the allegations:
The defendant will assert that the prosecution witness Nigella Lawson habitually indulged in the use of Class A and Class B drugs in addition to the abuse of prescription drugs throughout the time that the defendant was employed in the household. This evidence is of substantial importance as it explains why Ms Lawson initially consented, or appeared to consent, to the expenditure as the defendants were intimately connected to her private life and were aware of the drug use which she wanted to keep from her then-husband Charles Saatchi.
The statement added that the alleged illicit use of drugs "goes directly to her defence of actual or implied consent".
Last week, Ms Lawson told the court she had only taken cocaine on two occasions and that while she is "not proud of the fact ... [it] does not make me a drug addict or a habitual drug user".
Miss Grillo maintains that she was allowed to use the credit card for personal expenditure because she was "part of the family".
The Grillos, of Kensington Gardens Square, Bayswater, west London, each deny a single count of committing fraud by using a company credit card for personal gain between January 1 2008 and December 31 last year.
The trial was adjourned to 10am on Monday.