Rusal Calls for Investor Inquiry

　　MOSCOW -- A bruising shareholder dispute at OAO Norilsk Nickel escalated after United Co. Rusal Ltd. called on stock-market regulators to investigate Norilsk's largest shareholder, suggesting he controlled more stock in the company than he had disclosed. 　　Aluminum maker Rusal, which holds a 25% stake in Norilsk, one of the world's largest nickel producers, said in a statement that there were "a number of factors" indicating that billionaire Vladimir Potanin owned more than the just under 30% in Norilsk he is known to control. It called on the Federal Financial Markets Service, the market regulator, to investigate. 　　"This is a breach of Russian legislation," Rusal said in the statement. In a second statement, Rusal blamed Mr. Potanin's management policy for "poor production and financial performance." 　　Mr. Potanin's holding company, Interros, declined to comment. 　　The regulator said it hadn't yet received a formal request from Rusal to investigate. A spokeswoman for Rusal said it planned to lodge a complaint in the near future. 　　Rusal's statements came on the eve of a Norilsk board meeting Friday to choose a new chief executive for Norilsk. Mr. Potanin has nominated Vladimir Strzhalkovsky, an ally of Russian Prime Minister Vladimir Putin. But Rusal opposes his nomination on the ground that he lacks experience in the sector. It said Thursday in the second statement that such appointments flouted corporate governance and inflicted "severe economic and reputational damage" on Norilsk. Still, Mr. Strzhalkovsky is nonetheless expected to be elected. 　　For months, Rusal has been vying with Mr. Potanin for control of Norilsk, a contest Rusal appears to be losing. The company, controlled by billionaire Oleg Deripaska, has said it wants to combine with Norilsk to forge a diversified mining titan like BHP Billiton Ltd. But Mr. Potanin has resisted Rusal's overtures, instead exploring other combination scenarios. 　　If it were revealed that Mr. Potanin did own more than 30% of Norilsk he could, under Russian law, be forced to offer to buy out all of Norilsk's minority shareholders. 　　--Alexander Kolyandr contributed to this article.