The Federal Arbitration Court in the Siberian city of Tyumen has ordered a new hearing in a lower court, lawyer Konstantin Lukoyanov told Reuters. The original suit was thrown out last year.

"Today's decision casts doubts over the domestic court system's ability to create a predictable and effective legal environment," Lukoyanov said, adding it "inflicts substantial damage on Russia's investment climate".

The ruling comes amid renewed hostilities between TNK-BP's co-owners, BP and a quartet of billionaire investors, that escalated last Friday when BP said it would seek to sell its stake after receiving expressions of interest.

A spokesman for the AAR consortium, which represents the shareholder quartet, declined to comment. The group had previously denied being a party to the minority shareholders' lawsuit against the British major.

The minority shareholders claimed that TNK-BP suffered financial losses because it had been excluded from a planned strategic alliance unveiled last year between BP and Rosneft.

No date for the hearings has been set.

(Reporting by Vladimir Soldatkin; Editing by Douglas Busvine)

• A Permanent Economic Emergency