Citigroup is to advise Millhouse Capital, a core shareholder in Sibneft, on how to exit the aborted $22bn merger with Yukos. Millhouse is an investment company controlled by Roman Abramovich, owner of the UK's Chelsea football club.

Citgroup provided a fairness opinion to Millhouse in April when Russian oil groups Yukos and Sibneft announced their merger. It formally completed in October but is now being scrapped following the arrest on charges of tax evasion of Mikhail Khodorkovsky, the chief executive of Yukos and its core shareholder.