In an annual general meeting trading update, WPP said that on a reportable basis, worldwide revenues were down by 3% because of the pound strengthening against both the US dollar and the yen. On constant currency terms, revenues are up by 1%.
Revenues in North America were up by 2% and in continental Europe they rose by over 3%.
Sir Martin Sorrell, group chief executive, said: "Our public relations and public affairs businesses are still being most impacted by the slowdown and to a lesser extent branding and identity, healthcare and specialist communications, although healthcare and direct have been more resilient. Advertising and media investment management has been less affected and information, insight and consultancy continue to show the most resilience."
WPP Group is in the middle of a heated battle to take control of rival ad group Cordiant Communications. The takeover looked a done deal when Cordiant agreed to a £266m bid, but Active Value, one of Cordiant's biggest shareholders, is refusing to stop fighting and continues to increase its stake in Cordiant.
In today's statement, Sir Martin said that WPP is planning a radical redesign of the company's office space, and to develop cross-branding in areas such as healthcare, new technologies, new markets, privatisation, internal communications, retailing, financial services, and entertainment and media.
Sir Martin also reminded the company's investors that WPP's business was built on what he called the "wit, intelligence, imagination and enterprise of individual men and women".
He said that the individuals who work for WPP companies had been challenged as never before over the last three years. "And for three years now, they have responded magnificently," he said.
"On your behalf, and on behalf of the board, we thank them, salute them -- and devoutly wish them a more benign tomorrow."
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