International celebrity chef Nigella Lawson has been accused of using cocaine by her former assistant Elisabetta Grillo.

The allegations were made by the 41-year-old at Isleworth Crown Court here in the ongoing fraud trial against Lawson, 53, and her sister Francesca, 35, who are accused of spending around 685,000 pounds on company credit cards, reports a portal.

Grillo stated that she first saw the "Nigella Kitchen" host using the drug while she was married to late John Diamond, who died in 2001.

"I was cleaning and I noticed a little packet on top of the toilet. It was a little funny envelope. I saw white powder. I saw cash, like 20 pound notes, rolled up and once noticed a credit card with white powder and a CD with white stuff on," Grillo said.

She also claimed that Lawson would smoke cannabis in front of her children, Cosima and Bruno.

"They said she was smoking cannabis with them. She couldn't sleep so she'd go downstairs and smoke. They'd say that was helping mama," Grillo said.