The document also said competition enforcers were considering regulating the behaviour of dominant companies as a preventive measure, a move that would address concerns that regulatory actions sometimes come too late to repair the harm suffered by smaller rivals.

The proposed enquiry comes on top of other legislation planned this year aimed at reining in the powers of dominant companies and helping European companies to compete more effectively with them as well as with Chinese rivals.

The document said the enquiry would focus on "new and emerging markets that are shaping our economy and society".

The Commission's competition arm has over the last two decades opened enquiries into sectors ranging from e-commerce to pharmaceuticals, financial services and energy, which subsequently resulted in investigations into individual companies and hefty fines.

The document said a tougher line was needed to deal with certain platforms that act as large private gatekeepers and rule-setters to markets and information because competition rules alone were not sufficient.

"Additional ex ante regulatory responses may be needed to ensure contestability and protect the interests of smaller players," the document said.

European Competition Commissioner Margrethe Vestager, who has taken a tough line against Google, Apple and other dominant

tech companies, is due to present the paper next month.

(Writing by Foo Yun Chee. Editing by Jane Merriman)

By Gabriela Baczynska