Claims made by a US Treasury official that the US considers Russian President Vladimir Putin to be corrupt amount to an "official accusation", suggests The Kremlin in Moscow. In a forthcoming Panorama documentary for the BBC, Adam Szubin, acting US Treasury secretary for terrorism and financial crimes, said that Putin "has long-time training and practices in terms of how to mask his actual wealth".

Russian Presidential spokesman Dmitry Peskov told journalists: "It's an official accusation." He also said: "[Bilateral] relations are now in such a state that a lie like this is unlikely to aggravate them even further."

In the wake of the annexation of Crimea, the US imposed a series of economic sanctions on Putin's inner circle but it is the first time the US is believed to have accused Putin himself of corruption.

Szubin, who oversees the US sanctions regime, said: "We've seen him enriching his friends, his close allies, and marginalising those who he doesn't view as friends using state assets. Whether that's Russia's energy wealth, whether it's other state contracts, he directs those to whom he believes will serve him and excludes those who don't. To me, that is a picture of corruption." The official would not comment on a 2007 CIA report that put Putin's wealth at $40 bn (£28bn), but said that Putin had been amassing secret wealth.

"He supposedly draws a state salary of something like $110,000 a year. That is not an accurate statement of the man's wealth, and he has long time training and practices in terms of how to mask his actual wealth."

In response to claims aired in the film, Putin's spokesman said "none of these questions or issues needs to be answered, as they are pure fiction".