Publicis Groupe has bought digital agency Digitas for $1.3bn (£660m) – the biggest deal in the industry since WPP bought Grey for $1.75bn (£890m) last year.

Publicis says in a statement that both boards have unanimously approved the offer of $13.50 (£6.90) per share. Its chairman and chief executive Maurice Lévy (pictured) said earlier this year that he was looking to make an acquisition in the digital space.

Digitas’ clients include General Motors and American Express. It will remain a separate division of the Publicis Groupe and continue to be run by chairman and chief executive David Kenny.

He says: “By joining Publicis Groupe, we are bringing together key assets and strengths in order to capture a larger share of a sector which is expanding dramatically.”

Once the deal goes through, digital will represent 34% of Publicis Groupe’s revenue – an increase of 6%.

Lévy adds: “This operation will constitute a powerful growth engine for all of Publicis Groupe in a context in which digital and interactive marketing and communications should represent more than 10% of all worldwide investment by 2010.”