Rahul Gajjar, finance director for art dealer Mr Saatchi, told jurors at Isleworth Crown Court in west London that Elisabetta Grillo, aged 41, made the claim after he wrote to her and her sister about their alleged use of the couple’s credit cards to buy £685,000 (€820,000) worth of luxury goods for themselves.
Mr Gajjar told jurors that at first Elisabetta, referred to in court as Lisa, and co-defendant Francesca, aged 35, were open and apologetic about their spending spree.
But he said after he wrote each a letter outlining how the sisters would pay off their debt, they became “agitated”.
“Lisa was against the proposal and I remember a reference to ‘We’re being treated worse than Filipino slaves’,” Mr Gajjar said.
Mr Gajjar said Mr Saatchi and Ms Lawson, who divorced earlier this year, agreed that the sisters should continue working for them when the alleged offences came to light early last year.
He told jurors he suggested they continue on their current salaries with Francesca, who is alleged to have spent the £580,000 on herself, expected to pay back £1,000 a month, and Elisabetta £250 per month.
They would also be able to live rent-free at a flat owned by TV chef Ms Lawson in Battersea, central London, the court heard.
But Mr Gajjar said the sisters reacted angrily to this.
“They were absolutely in disagreement,” he said. “They felt it tied them to the company for the rest of their lives.”
The court heard a series of text messages exchanged by Mr Gajjar and Francesca, including one where she complained her membership at private club Soho House had been cancelled.
“If they carry on doing stuff like this, I won’t have any choice but to go to court,” she wrote.
Mr Gajjar said that when he later spoke to Elisabetta on the phone about the letter, which she refused to sign, she became “hysterical” and “in a rage”.
“She said that she wanted no one to get in touch with her or her sister,” he said.
Anthony Metzer, defending Elisabetta, suggested this was because the sisters were under the impression they could use the credit cards on themselves and the matter was a misunderstanding.
The court previously heard that Mr Saatchi alleges that Ms Lawson was so high on drugs she was unaware of what she had or had not permitted the defendants to spend money on.
Mr Metzer said: “Until now, until this letter, there had never been any mention had there, by you or by anybody, of dishonesty.
“This is the first time in which the suggestion of fraud or dishonesty has come from you in any way whatsoever?”
“On a formal basis, yes,” Mr Gajjar replied.
“This is ‘you are a fraudster’,” Mr Metzer said. “This was in a different league wasn’t it?”
“Yes,” Mr Gajjar said.
The court heard that both defendants were given credit cards in Mr Saatchi’s Conarco Partnership account with Coutts bank to buy items for the household.
Mr Gajjar told jurors he found out about the alleged fraud after noticing that Francesca’s average monthly spend on her card was £48,000, while Elisabetta’s was £28,000. The other personal assistants employed by Mr Saatchi had a maximum average spend of £8,000, while the average amount Ms Lawson herself spent on her card per month was just £7,000.
The Grillos, both of Kensington Gardens Square, Bayswater, London, deny the charge against them.
It is alleged that, between Jan 1, 2008, and Dec 31, 2012, they committed fraud by abusing their positions as PAs by using a company credit card for personal gain.