One of the personal assistants accused of defrauding Nigella Lawson and Charles Saatchi has told a court the TV cook allowed their children to smoke cannabis.

Elisabetta Grillo, 41, who also accused the celebrity couple of lying under oath, told jurors Ms Lawson permitted the teenagers to smoke the Class C drug as she gave evidence in her fraud trial.

The defendant, who along with her sister Francesca Grillo, 35, is accused of spending £685,000 on credit cards belonging to the celebrity couple to buy designer goods and luxury holidays for herself, made the allegations as she spent a second day in the witness box at Isleworth Crown Court in west London.

Elisabetta, 41, was asked by prosecutor Jane Carpenter to explain a duty-free transaction for £69.71 in New York in June 2010.

"It was cigarettes for the children. I bought them and Nigella allowed me to buy them," Grillo said.

"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 underage children?"

Grillo said: "Well, if Nigella Lawson let the children smoke weed..."

The defendant tailed off as Judge Robin Johnson interrupted the exchange.