This compared with growth of 6.3% for WPP's worldwide revenues, once currency fluctuations are excluded.
Global revenues declined by 0.7% year on year, which the group blamed on the 11% decline in the US dollar against the British pound.
The strongest growth came from WPP's interests in the emerging markets of Asia Pacific, Latin America, Africa and the Middle East.
Martin Sorrell, WPP chief executive, reported that revenue from advertising and media assets dropped 2.2% year on year, but this equated to a rise of 4.5% in constant currency terms.
The fastest growing divisions were public relations and public affairs, up 12.9% in constant currency terms; and branding and identity, healthcare and specialist communications, up 9.6% on the same basis.