Speculation is mounting that the Swiss government is planning to sell its stake in UBS as soon as the “lock-up” period on the SFr6bn ($5.4bn) state investment in the beleaguered bank expires next month.

The government can sell the mandatory convertible notes, which were issued as part of its bail-out of UBS last October, when the lock-up period expires on June 9. The move would give the state a 9.3 per cent stake in UBS