Existing shareholders would hold 50 per cent of the shares of the combined firm, the companies said
Publicis chief Mauris Levi and his Omnicom counterpart, John Wren, are to become co-chief executives of the new concern with an estimated market value of 35 billion dollars.
The merger would bring BBDO Worldwide (Ommocom) and Saatchi & Saatchi (Publicis) under one roof. It will also see WPP outranked as world leader in advertising and marketing services.
Omnicom and Publicis together had 23 billion dollars in revenues in 2012.
Their collaboration could put pressure on an already battered media industry. The sheer size and global reach of the new entity could help to drive down the cost of television and online campaigns as well as newspaper and magazine advertising.
The deal requires approval from regulators.