The US Treasury has told a BBC investigation that it considers the Russian leader, Vladimir Putin, to be corrupt.

Though the US government has already imposed sanctions on Kremlin insiders, this is thought to be the first time they have directly accused Mr Putin of corruption.

Panorama investigated Mr Putin's private finances and spoke to those who say they have inside knowledge of his secret fortune.

Richard Bilton reports.

Panorama: Putin's secret riches, BBC One, 8.30pm, Monday 25 Jan.