Publicis, the French advertising giant, stands to generate about a quarter of its revenues from digital platforms after winning the battle for Razorfish, the second-largest digital advertising agency in the United States.

The $530 million (£320 million) takeover will expand Publicis’s presence in high-growth areas such as social networks and intensifies the battle for online business against WPP and Omnicom, its rivals.

Razorfish, valued as high as $6 billion during the technology boom, was put up for sale by Microsoft, which bought it as part of the $6 billion acquisition of aQuantive in 2007.

Publicis, which owns the Saatchi & Saatchi agency, saw off competition from WPP and Dentsu, of Japan. Microsoft will take a stake in Publicis as part of the conditions of the sale.

The deal firmly nails Publicis’s colours to the digital mast and follows its acquisition of Digitas in 2007 and its partnership last year with Google, which dominates online advertising.

Alex de Groote, an analyst with Panmure Gordon, said that the American company represented the last “big fat fish” in the digital advertising sector and that the deal had raised the stakes in the battle for clients looking to advertise online. “Digital media is going to be an increasingly large piece of the pie. To benefit from that, you have to have scale and you have to have the right assets,” he said.

Thomas Singlehurst, an analyst with Citigroup, said that, while WPP had held a strong foothold in online advertising for some years, the acquisition of Digitas and Razorfish left Publicis well positioned. “With relatively little investment, Publicis have been able to replicate that strength,” he said.

For WPP, Razorfish may have been seen as too big a target after last year’s £1.1 billion acquisition of Taylor Nelson Sofres and its $650 million purchase of 24/7 Real Media, the internet advertising specialist, in 2007.

Industry commentators suggested that WPP may have been put off by the high price, as well certain media-buying guarantees agreed with Microsoft over the next five years.

One said: “I’m mystified at the price that has been paid,” adding that Microsoft appeared to be in an “unholy rush to get the deal done”, possibly because of an impending series of retention bonuses due to Razorfish staff.

Nevertheless, analysts were broadly comfortable with the price of the acquisition.

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