Revenue rose over the first six months of the year by 6% to £2.03bn, while turnover was up 6% to £9.1bn. Operating profit increased by 13% to £264.7m and was up more than 21% in constant currencies.
Profit before tax rose by almost 16% to £234.7m from £202.9m in the last period and was up more than 25% in constant currencies.
All regions except continental Europe showed double revenue growth in the first half of 2004, but WPP said there were signs of improvement in the region. UK revenue was up 12% compared with 11% in North America.
WPP, headed by chief executive, Sir Martin Sorrell, said there was significant improvement for the group compared with 2003 and 2002.
However, WPP was concerned about the prospect for the US economy after the presidential election. It said the winning candidate would have to deal with a substantial fiscal deficit, a weak dollar and risks of inflation.
The group said it was aiming for a 14% headline operating margin in 2005 and it will set a target of 15% for 2006.
The company's share price fell by 21% over the period as WPP considered making a bid for rival advertising giant Grey Global Group. WPP is carrying out due diligence but earlier this week the investment bank Morgan Stanley said it did not believe WPP would bid for Grey.
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