Portugal's public deficit is expected to reach 6.7 to 7.1 percent of output for the first half of this year, far off the government's target of 4.5 percent, experts commissioned by parliament said.
"If this forecast is confirmed, the expected budgetary consolidation measures will not be sufficient to meet the budget deficit target" of 4.5 percent of GDP for year end, the report sent to Portuguese parliamentarians said.
The experts blamed sharply lower tax revenues for the gap, said the agency Lusa.
Their report came after official figures on Thursday showed that the government would probably miss its target of cutting the public deficit to 4.5 percent of output this year unless it found ways to tighten the budget further.
Like many heavily-indebted eurozone countries, Portugal is in an economic recession exacerbated by sharp budget cuts which took effect starting in May 2011 as Lisbon was granted a bailout worth 78 billion euros ($97 billion).
Representatives of Portugal's international lenders -- the European Union, the International Monetary Fund and the European Central Bank -- on Tuesday began their fifth mission to assess the austerity reforms pledged by Lisbon in exchange for the aid funds.
The Portuguese economy is forecasted to contract 3 percent this year, while unemployment, currently at 15 percent, is at a record high.