Nigella Lawson spent almost £55,000 at Donna Karan over a four-year period and paid more than £7,500 for a custom-made sofa, according to one of her personal assistants.

Zoe Wales, a member of Lawson’s inner circle – dubbed Team Cupcake – told Isleworth crown court that the celebrity TV cook and her ex-husband, Charles Saatchi, also spent £2,250 on cashmere jumpers and £1,368 on a one-off order of wine from an exclusive London cellar.

Wales was giving evidence at the trial of two of Lawson’s former personal assistants – Elisabetta and Francesca Grillo – who are accused of spending £685,000 on the family’s accounts without authorisation.

Prosecutors claim the sisters lived the “high life” by splashing out on designer clothes and handbags from Louis Vuitton, Christian Dior and Vivienne Westwood. They have claimed the spending was authorised by Lawson as part of a tacit understanding that they would not tell Saatchi about Lawson’s allegedly heavy use of cocaine and cannabis.

Last week, Lawson told Isleworth crown court that she had taken cocaine when her first husband was dying and again in 2010, arguing that on those occasions she did not have a drugs problem but “a life problem”. She also admitted smoking cannabis in the last year of her marriage to Saatchi, but added: “The idea that I am a drug addict or a habitual user of cocaine is completely ludicrous.”