BRUSSELS, Dec 5 (Reuters) - Lobby group Japan Association of New Economy has joined U.S. Big Tech to warn against proposed EU cybersecurity labelling rules that they said could hamper their access to the bloc's markets, according to a letter sent to the EU industry chief.

The European Union wants to set up an EU certification scheme (EUCS) to vouch for the cybersecurity of cloud services and help governments and companies in the bloc to select a secure vendor for their business.

A requirement that Amazon, Alphabet's Google, Microsoft and other non-EU cloud providers set up a joint venture with an EU-based company to qualify for the EU cybersecurity label has triggered criticism from some EU countries and foreign vendors.

The Japan Association of New Economy also slammed these requirements.

"It could create a de facto market access barrier, hurting both EU and Japanese companies," its director Hiroshi Mikitani wrote in a Nov. 28 letter to EU industry chief Thierry Breton seen by Reuters.

"We believe that the EUCS should be revised in light of the EU-Japan Digital Partnership, the Japan-EU mutual adequacy arrangement, and the Agreement in Principle on Negotiations Concerning Provisions on the 'Free Flow of Data' under the Japan-EU Economic Partnership Agreement," he said.

The Commission had no immediate comment.

The Japan Association of New Economy is a business lobby group focused on e-business and developing new industries. It counts a number of high-profile business leaders among its ranks and is headed by Mikitani, who is chief executive of Japanese e-commerce and fintech firm Rakuten. (Reporting by Foo Yun Chee in Brussels and Dave Dolan in Tokyo, editing by Miral Fahmy)