The UK returned a weak performance compared with other markets, recording organic growth of 1.9%, compared to Europe's 2.9%, North America's 5.8% and worldwide growth of 11.9%.
During 2005, WPP media agencies MindShare, Mediaedge:cia and MediaCom generated estimated net new billings of £1.6 billion globally.
The report on the results mentioned the network's local difficulties in Italy, where country manager Marco Benatti was personally dismissed by WPP chief executive Sir Martin Sorrell.
The report states: "In January 2006, the contract of the Group's Italian country manager was terminated and an investigation initiated into certain aspects of the Group's operations there. Legal action against the former country manager has commenced. It is not expected that this will have a significant effect on the Group's financial results."