(Reuters) - WPP ( WPP ) named former BT chief Philip Jansen as its new chair on Tuesday, succeeding Roberto Quarta at the world's largest advertising company.

Jansen will join WPP's ( WPP ) board in September and replace Quarta, who has been in the role since 2015, on Jan. 1.

The appointment comes at a time when WPP ( WPP ), which owns the Ogilvy and GroupM agencies, became a clear laggard among global ad companies with an organic revenue drop in the first quarter, hurt by less spending from tech clients, a downturn in China and the loss of business from Pfizer.

"(Quarta) has helped to steer the company through significant challenges including the Covid-19 pandemic, overseen the restructuring of our portfolio to return WPP ( WPP ) to financial stability, and guided the fundamental reshaping of our offer to meet the needs of modern marketing," WPP ( WPP ) CEO Mark Read said.

Jansen left BT earlier this year.