Sir Martin Sorrell, chief executive of the former largest media group in the world, WPP, has voiced doubts over the Publicis-Omnicom merger that shocked the world on Monday morning, describing the move as a "big opportunity" for his agency.

Media giant Omnicom have announced a rise in pre-tax profits of $482 million (£316.7 million) in the three months to the end of June 2013, up 2.3% on Q2 in 2012.

Global advertising and marketing monolith Omnicom Group posted a 12.9% rise in fourth-quarter profits, with net income breaching $300m.