A merger this complex could turn out to be a nightmare, particularly given how little time UBS has had.

While the government's commitment cannot be overturned, the vote marks a symbolic rebuke for the authorities, whose decision to largely bypass the nation's legislative has angered many politicians.

Last month, Swiss authorities announced that UBS would buy Credit Suisse in a shotgun merger to stem further banking turmoil after the smaller lender had come to the brink of collapse.

Last month, Swiss authorities announced that UBS would buy Credit Suisse in a shotgun merger to stem further banking turmoil after the smaller lender had come to the brink of collapse.

Finma says its main focus is on 'the transitional phase of integration' and 'preserving financial stability'.

Some investors, including a large mutual fund group that also runs a hedge fund, said prospects for banks had gotten progressively worse in recent months given the economic outlook.

The takeover creates a banking giant such as Switzerland has never seen before – and raises concerns about possible layoffs.

UBS would require public guarantees to cover legal costs and potential losses, according to a report by Bloomberg, citing anonymous sources.