Switzerland's accounts for the year 2000 have closed with a surplus of SFr4.5 billion ($2.74 billion) instead of a forecast deficit of SFr1.8 billion.
The finance ministry said on Monday that+ the difference was due to exceptional income and did not mean a balanced budget was guaranteed in future.
It said the surplus was due to the strong economic growth last year and certain unforeseen events, such as company mergers.
Spokesman Daniel Eckmann confirmed the figure for the budged surplus put forward by the French-language business newspaper, L'Agefi, but denied the finance ministry had been trying to conceal the exceptional result.
He said the ministry has been revising its forecast income upwards since last October, when it first admitted a surplus was expected.
However, in December, the finance minister, Kaspar Villiger, suddenly put on hold a series of tax cuts which had been approved by parliament. He warned that a balanced budget in the long-term was not assured.
In mid-January, the ministry said the surplus was likely to reach at least SFr2 billion, and announced the launch of an internal inquiry into how the experts prepare their forecasts.
But its admission only two weeks later that it will be more than twice as big is certain to lead to further criticism of the ministry's failure to be more accurate. Analysts say it is also likely to result in a political battle over how to spend the unexpected windfall.
swissinfo with agencies