The commission approved the merger "without condition", giving the go-ahead for the creation of Publicis Omnicom Group, bringing together $23 billion (£15 billion) in revenue and more than 40 per cent of the global ad market.
The impending deal has also been approved in Omnicom’s home market of the US, and has also been cleared by regulatory bodies in Australia, Brazil, Canada, Columbia, India, Japan, Mexico, Russia, South Africa, South Korea, Turkey, Ukraine, Omnicom and Publicis said in a statement.
It still has more hurdles to clear, including merger control approval in China, registration of the transaction in the US, initiating stock exchange listings and passing some European securities regulations.
The merger will also have to be approved by the shareholders of both Publicis and Omnicom, before it can be complete.
The deal was expected to go through in Q1 this year, but its completion is likely to be delayed until the second quarter.
Omnicom and Publicis, the second- and third-largest holding companies respectively, announced plans to merge in July 2013. The new holding company created from their alliance will overtake the world’s current largest group, Martin Sorrell-led WPP.
The new group will have more than 135,000 employees and bring together Omnicom and Publicis networks covering advertising, media, digital, PR and DM.
Omnicom’s networks include BBDO, DDB and TBWA, as well as Omnicom Media Group, which incorporates both OMD and PHD.
Publicis Groupe, which is based in France, operates the Publicis Worldwide, Saatchi & Saatchi and Bartle Bogle Hegarty advertising networks, media agencies including Starcom MediaVest and ZenithOptimedia, and digital agencies Razorfish and Digitas LBi.
Omnicom and Publicis hosted their first joint management meeting in October 2013. The European Commission was notified about the deal on 25 November 2013.