UBS stood firm yesterday, refusing to give further aid to the US government in its quest to reveal secret offshore bank accounts.

UBS official Mark Branson said the bank “has now done all that it can do to cooperate” with the IRS request.

“UBS cannot disclose information to the IRS that would put its employees at serious risk of criminal prosecution under Swiss law,” said Branson, who is the chief financial officer of the bank’s global wealth management and Swiss bank division in Zurich.

This comes despite US claims that up to 52,000 Americans may have undisclosed accounts at the giant Swiss bank.

A Senate Homeland Security and Governmental Affairs Committee heard how UBS activity “actively facilitates tax evasion (and) amounts to a declaration of war by offshore secrecy jurisdictions against honest, hardworking taxpayers,” (Sentaor Carl Levin)

UBS has already disclosed around 300 names and paid a $780 million fine to the US government. Disclosing further offshore bank accounts would seriously damage Switzerland’s business prospects as a jurisdiction famous for is bank secrecy.

The Swiss government is giving UBS financial aid to help it through the financial crisis and has also set up a crack team of legal and diplomatic experts to defend bank secrecy’s role in modern finance against recent calls for greater transparency.