Portugal's National Statistics Institute estimates the debt-stressed country's national budget deficit last year was 8.6 percent — far above the government's target of 7.3 percent.
The estimate published Thursday was another severe setback for Portugal's attempts to avoid taking a bailout as Greece and Ireland had to last year.
Portugal has been overwhelmed by a financial crisis that has pushed the yield on its 10-year bond to a euro-era record of 8.23 percent, an unsustainable level.
The government quit last week in a dispute with opposition parties over measures to restore the country's fiscal health.
Rating agencies have downgraded the country's credit worthiness three times in recent days.