Sorrell hinted at the decision as part of WPP's full-year results this week, but is expected to reveal specific investment plans next month.
In a statement to investors, he said one of the company's long-term strategic priorities was to "develop the faster-growing functional areas of marketing services, particularly direct, interactive and market research".
Sorrell praised the performance of information and consultancy agencies such as Millward Brown, which enabled revenues in this area of WPP's business to grow by 4% in 2002, compared with an 8% drop in PR revenues and 0.2% growth in branding, healthcare and specialist communications. Advertising and media management, the traditional heart of the WPP group, grew by 2.5%.
WPP blamed the long-lasting ad recession on an overall 3% drop in revenues to £3.9bn and a 50% plunge in pre-tax profits to £205.4m.