The US banks creating a $75bn-plus “superfund” to buy the assets of troubled investment vehicles should sell 10 per cent of the fund into the open market to ensure it is properly priced, the renowned investor Warren Buffett said on Thursday.

The billionaire is the latest leading figure – including Alan Greenspan, former chairman of the Federal Reserve – to pour scorn on the fund promoted by Citigroup, Bank of America and JPMorgan Chase with the US Treasury’s encouragement.