Maurice Levy: 'A lot of our clients ask if they should move their corporate headquarters to continental Europe' because of Brexit

Publicis Groupe CEO Maurice Levy said he believes Brexit will be a "nightmare" of uncertainty for Britain. The ad agency holding company chief was speaking at Web Summit in Lisbon today, in front an audience of about 2,000.

"We are seeing a lot of our clients ask if they should move their corporate headquarters to continental Europe," he said. The main effect of the Brexit vote has been to prevent companies from making decisions about the future, he said, which could put economic growth on hold. "Our clients are in a wait-and-see situation, which is not good."

"The uncertainty is not good for the economy ... it's not good for job creation."

Publicis owns such famous agency brands as Saatchi & Saatchi and Leo Burnett. Its biggest clients include Coca-Cola, Citigroup and Heineken.

"I guess no one had a clear idea of the nightmare it will be."

"There are something like 80,000 pages of treaties to be negotiated," Levy said, calling it "an absolute nightmare." Publicis has no plans to retreat from the UK, he added.

"If the UK wants to keep the financial services, the financial passport, they will have to accept something that has been rejected by the voters - free circulation" of people across borders, Levy predicted.

There is only one bright side, Levy said in a conversation on stage at Web Summit with Business Insider, and that is the devaluation of the pound.

"As a matter of fact due to the devaluation of the pound there are some acquisitions that are starting to become more attractive. They are costing us less."