The allegation came into light during a pre-trial hearing in London where her two former assistants, Francesca and Elisabetta Grillo, were charged with stealing money from her former husband Saatchi over 300,000 pounds to spend on luxury items and holidays, reported Sun online.
Francesca and Elisabetta told the court on November 26 that Lawson used cocaine, cannabis and prescription pills daily for a decade.
The sisters said that Lawson authorised the use of Charles' company credit card for their personal use in exchange for their understanding to keep silence on the issue.
Prosecuting lawyer Jane Carpenter said, "This is a totally scurrilous account which has been raised by the defence, and the timing is no coincidence at all.