In a joint statement, chairman Douglas Flint and chief executive Stuart Gulliver claimed concern was growing among stakeholders, but insisted the financial firm remained committed to the City.
"We are ... being increasingly asked by shareholders and investors about the likely additional cost of being headquartered in the UK," they said. "We are very clear that the City of London's competitive position deserves protection."
The pair added that talk of a move elsewhere was "speculative", but implied they had received assurances from the British government that it would seek to ensure London remains one of the world's top financial centers.
UBS chief executive Oswald Grubel last week lashed out at UK authorities in an interview with the Financial Times, suggesting politicians had done little to scale back their anti-bank rhetoric.
By Claire Archer