Sir Martin Sorrell has launched a stinging attack on WPP, the FTSE 100 advertising group from which he split acrimoniously last year following allegations he used company money to pay a prostitute.

In an exclusive interview with Financial News, the 74-year-old industry veteran, who is still a large shareholder in WPP, said his successor, Mark Read, has made some “terrible mistakes” while at the helm of the world’s biggest advertising company.