BRUSSELS — A top Russian official on Wednesday sharply criticized European Union rules aimed at making the bloc’s energy market more competitive, suggesting that they could jeopardize a giant pipeline project called South Stream.

Sergei I. Shmatko, the Russian energy minister, said that if companies behind projects like South Stream were “deterred from initiating them or face restrictions over the returns they can expect on their investments, the result will be detrimental, above all to the interests of consumers.”

South Stream, which sponsored the event where Mr. Shmatko spoke, is backed by Gazprom, the Russian state-owned natural gas monopoly. The pipeline would run under the Black Sea, bypassing Ukraine to supply customers in Europe. It is a rival to Nabucco, a project backed by the European Union.

The minister was criticizing E.U. legislation that includes rules forcing energy companies to share their infrastructure with competitors. Mr. Shmatko said that intensive talks were under way with the European Commission, which is the E.U. executive branch, and that he expected a decision by autumn on how those rules and others would apply to South Stream.