The nationwide investigation into the collapsed auction-rate securities market intensified on Thursday as Andrew Cuomo, the New York attorney general, filed civil charges against UBS, accusing the Swiss bank of selling the investments while falsely marketing them as safe and liquid.

In a complaint filed on Thursday, Mr Cuomo claimed that the Swiss bank stepped up efforts to sell the securities to its retail customers “so as to reduce its own exposure”. The filing said that several senior UBS officials, who are not named, sold more than $21m of their personal holdings of auction-rate securities.