Russian investigators have charged economy minister Alexei Ulyukaev with extorting a $2m bribe from state oil group Rosneft, as struggles over policy and power in President Vladimir Putin’s administration escalate.

Mr Ulyukaev, a vocal proponent of liberal economic reform, is the most senior government official to be detained in office since the collapse of the Soviet Union in 1991.

The Investigative Committee, the federal institution that probes large crimes, said Mr Ulyukaev was detained on Monday while receiving the bribe. He had demanded money from Rosneft for a positive evaluation by his ministry, which allowed Rosneft to go ahead with a deal to acquire a 50 per cent stake in smaller state oil producer Bashneft, the committee said. A Moscow court yesterday put Mr Ulyukaev under house arrest for two months, granting an investigators’ request.