Under pressure from the US government to divulge more information about secret accounts, Switzerland’s largest bank is standing its ground.Under fire at a Senate hearing, a representative of the UBS bank refused to disclose the names of tens of thousands of rich American clients. US authorities suspect they have been using secret Swiss bank accounts to dodge paying taxes at home. “We made a good faith effort to produce responsive information available in this country that could be disclosed without violation of Swiss law,” said senior UBS executive Mark Branson. “But UBS cannot disclose information to the IRS that would put its employees at serious risk of criminal prosecution under Swiss law.” UBS argues the data sought by the Americans is protected by Swiss financial privacy legislation. But last month it acknowledged responsibility for helping US clients conceal assets. UBS also agreed to pay a hefty fine and to identify some American customers in a deal that resolved criminal fraud charges.