Andrew Cuomo, the New York Attorney-General, is preparing to file civil securities fraud charges against UBS, according to media reports.

Meanwhile, the Zurich-listed bank, beset by legal cases in the US and $38 billion in credit market write-downs, has been warned by Texas' top securities regulator that it will ban UBS from doing business in the state until investors who bought auction rate securities from the Swiss bank get their money back.

In New York, Mr Cuomo may file charges, which relate to the Swiss bank's participation in the auction rate securities market, in the next few days, according to The Wall Street Journal.

Auction rate securities are short-term financial instruments that investors hold as an alternative to cash. Mr Cuomo’s charges will relate to whether UBS gave investors sufficient warning that the securities, which are generally easy to sell, can become illiquid.

The $330 billion market, in which charities, student loan companies and other institutions issue the securities via investment banks, collapsed in February leaving thousands of investors unable to sell their holdings.

The Massachusetts securities regulator has already filed charges against UBS relating to the auction rate securities market.

The WSJ said that the New York case may also include charges against individual bankers, which was not a feature of the Massachusetts case.

UBS said it would be "disappointing" if Mr Cuomo filed a complaint because the bank was working with regulators and peers to find a solution to the auction rate issue.

UBS is also under fire from US tax authorities, which claim the bank’s advisors helped wealthy American clients evade taxes.

In the Texan case, the Texas State Securities Board said that UBS engaged in fraudulent conduct by misrepresenting auction-rate securities as “liquid investments” and a “cash alternative.”

UBS employs 800 people and has about $65 billion of assets under management in its wealth management business in Texas.