File photo of Martin Sorrell who has quit as chief executive of WPP less than a fortnight after the world's biggest advertising group revealed it had launched an independent investigation into allegations of misconduct against him

London (United Kingdom) (AFP) - Martin Sorrell quit Saturday as chief executive of WPP, the world’s biggest advertising agency, following allegations of personal misconduct through the misuse of company assets.

Sorrell, who founded the British ad giant and has been at the helm for the past 33 years, stepped down less than a fortnight after the group launched an independent investigation into the allegations.

WPP said the probe had concluded, adding that “the allegation did not involve amounts that are material”.

Sorrell, 73, said in a statement that he was sad to leave, with WPP having been his passion and focus for more than three decades.

“As I look ahead, I see that the current disruption is simply putting too much unnecessary pressure on the business, our over 200,000 people and their 500,000 or so dependents, and the clients we serve in 112 countries,” he said.

“That is why I have decided that in your interest, in the interest of our clients, in the interest of all shareowners, both big and small, and in the interest of all our other stakeholders, it is best for me to step aside.”

WPP said Sorrell will be treated as having retired, with chairman Roberto Quarta becoming executive chairman until a new chief executive has been appointed.

Sorrell denied any wrongdoing after the allegations surfaced earlier this month, but said he understood the company had to investigate it.

Sorrell has made headlines in recent years regarding his sizeable pay at a time when traditional advertising groups struggle against fierce competition from the likes of Google and Facebook.

He received a knighthood from Queen Elizabeth II in 2000.