Rio Tinto Group (ASX:RIO) has been accused of political bribery in a secret lawsuit involving its Oyu Tolgoi copper mine in Mongolia, the Australian Financial Review reported Sunday, citing details obtained on the allegations filed on May 20.

The dispute has persisted for nearly two decades, with company and Mongolian officials squabbling over the mine's wealth, AFR reported.

The Mongolian government's decision to file the lawsuit in a British court suggests the tension has not been resolved despite outgoing Chief Executive Jakob Stausholm spending nearly AU$8.5 billion on buying out minority shareholders and waiving government debts.

The lawsuit aims to force the company to produce evidence, helping Mongolia argue its case in the arbitration, the report said.

While Mongolian authorities directly accuse the company and its subsidiaries of corruption and bribery, there is no suggestion that Stausholm was involved in the incidents, which took place between 2008 and 2012, or that the lawsuit led to his resignation, according to the report.

Rio Tinto did not immediately respond to a request for comment by MT Newswires.

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