"Switzerland ought not to be a financial centre for tax evaders. The financial sector cannot become involved in tax crimes," said Kaspar Villiger, chairman of the board at UBS, in prepared remarks for the bank's annual general meeting.
"For years, banking confidentiality was a key part of the Swiss financial centre's appeal," he added.
"Other states are no longer prepared to accept their citizens evading tax in this way. This paradigm shift occurred unexpectedly quickly and with enormous force. Switzerland was forced on the defensive and has had to ward off attacks from all sides.
"Banking confidentiality is increasingly losing its legitimacy."
Switzerland has come under attack in recent years for the secrecy of its banking sector and charges it helped foreign clients evade taxes at home.
Prosecutors in France are investigating whether UBS helped French nationals dodge taxes, and officials in the United States are investigating 11 Swiss banks on suspicion they encouraged their clients to channel undeclared assets into Swiss accounts.
The US already forced UBS to pay a $780-million fine and hand over details on more than 4,000 clients in a 2008 tax evasion case, and in January indicted three Swiss bankers accused of hiding $1.2 billion in assets.
Switzerland has recently signed deals with Austria, Britain and Germany to toughen up penalties on tax cheats.
Villiger, who is set to step down and be replaced by ex-German central bank chief Axel Weber at the meeting, endorsed the idea of a final withholding tax -- the deal negotiated with Austria, Britain and Germany -- but rejected automatically exchanging bank information with other countries.
"Swiss banks must not serve as the extended arm of foreign tax authorities," he said.
He also insisted deals with other countries put all old grievances to rest.
Switzerland "must not accept a solution which provides no reasonable means of regularising the past," he said.