MOSCOW, October 12 (RIA Novosti) - The Russian president's economic adviser sharply criticized Wednesday the two biggest deals in the country's corporate history.

Andrei Illarionov, who is known for his critical views of government policy, slammed natural gas giant Gazprom's purchase of a 72.7% share in Sibneft, the country's fifth largest crude producer, and state-owned oil company Rosneft's acquisition of Yuganskneftegaz, the former core production of embattled major Yukos, at the end of 2004.

"They are more than a crime - they are a mistake," he said.

He added that instead of allowing state-controlled companies to take over formerly private companies, Russia should fully privatize the energy sector. He also proposed that the government lift the "ring fence" around the country's energy sector and infrastructure to allow greater foreign investment.

Illarionov also criticized Economic Development and Trade Minister German Gref for his ambiguous position on the issue of state influence on the economy.

Speaking at an economic forum in Sochi last month, Gref described the idea of the state playing a greater role in the economy as "neanderthal" and said it must be buried. But on October 11, his ministry supported Gazprom's purchase of Sibneft's stake.