A secretive deal aimed at settling a dispute with Washington over Swiss banks' alleged complicity in tax evasion by Americans has caused uproar in the wealthy Alpine nation.
Swiss Finance Minister Eveline Widmer-Schlumpf announced a deal last week that she said would put an end to the row that has been poisoning relations between Switzerland and the United States for years.
However, she acknowledged, the settlement was not a negotiated agreement but a "unilateral offer" from Washington, and due to a confidentiality clause, no details of the deal could be divulged until parliament had given it its blessing.
She urged parliament, which has no power to amend the agreement, to urgently debate the issue, stressing the importance of the deal taking effect by July 1.
Swiss parliamentarians however balked at the idea of discussing the issue without knowing what conditions were attached, and on Wednesday, the lower house of parliament voted to freeze its handling of the deal until it had more information.
"We understand that the National Council is demanding more information about the offer from the US authorities," the Swiss Bankers Association told AFP in an email.
But, stressed the group which represents nearly 350 banks and financial institutions, "it is important for the banks to have a legal basis before they act".
Washington has repeatedly accused Swiss banks of complicity in tax evasion, since they hold billions of dollars belonging to American citizens that are not declared to US tax authorities.
The controversial deal would enable Swiss banks to circumvent some elements of the country's cherished bank secrecy laws and turn over key information to US authorities.
How much the banks will have to pay to win legal closure is not yet known, but Swiss media have reported that the overall figure could hit 10 billion Swiss francs (NZ $13 billion).