Oleg Deripaska, the Russian billionaire whose meetings with senior British politicians have triggered controversy, faces fresh scrutiny about his company’s role in an alleged $500m fraud in Tajikistan, one of central Asia’s poorest countries.

Rusal, the aluminium group controlled by Mr Deripaska, was on Monday accused in the High Court of knowingly participating in a “grubby” scheme that allegedly divested Tajikistan’s most important industrial asset – a state-owned smelter not far from the country’s capital – of hundreds of millions of dollars. While neither Rusal nor Mr Derispaska are defendants in the high-profile proceedings, lawyers representing Tajik Aluminium Plant, now known as Talco, characterised them as important players in the alleged conspiracy.