LONDON - Aluminium giant Rusal obtained permission by a London court on Friday to add Russian billionaire Roman Abramovich and his firm Crispian Investments as defendants in the case against Vladimir Potanin, CEO of Nornickel.

The application marks the latest flare-up in relations between two of Russia's biggest metal companies.

Nornickel is the world's largest palladium producer and a major miner of refined nickel. Potanin holds a 37% stake in it, while Rusal holds 26.4% and former Chelsea Football Club owner Abramovich has a 4% stake.

The aluminium giant claims that Potanin violated a shareholder agreement signed in December 2012, causing losses for Rusal. Abramovich and his investment company Millhouse, later replaced by Crispian Investments, were parties to the deal.

Crispian Investments objected to Rusal's application, while Abramovich did not respond to it, said David Mumford, KC for Rusal at Friday's hearing.

Judge Sean O'Sullivan, however, ruled that Abramovich and Crispin could be added to the case, after the hearing.

"The joining of Crispian Investments Limited and Mr. Roman Abramovich as parties to the case is another step for the implementation of Rusal's claims against Mr. Vladimir Potanin and his company Whiteleave Holdings Limited," Rusal said in an emailed statement.

Potanin's Interros holding company declined to comment.

Nornickel has not been directly targeted by Western sanctions after Russia's invasion of Ukraine, but Britain has placed sanctions on Potanin and Abramovich.

Oleg Deripaska, founder of Rusal and also sanctioned by Britain, is not a party to the litigation.

The dispute that led to the lawsuit, first filed in October 2022, and Rusal's further claims, centre on the 2012 framework agreement between Nornickel's two largest shareholders, which protected dividend payouts among other things.

Disagreements over dividends and governance have been the main reason for on-and-off rows. At the time of the 2012 framework agreement, Abramovich helped to cool a dispute over how much profit should be returned to investors and how much should be invested in Nornickel.

Rusal alleges in court filings that Potanin "had overseen the transfer of crucial assets out of the NN Group (Nornickel) under false pretences and/or at undervalues to the advantage of himself and his associates, dishonestly procured the transfer out of ...the NN Group of hundreds of millions of dollars and mismanaged the NN Group, which has led directly to certain industrial accidents."