The Fiscal Advisory Council has said the weakening international growth outlook raises a question mark over the ability of the Government to hit its budget deficit target of 8.6% of GDP.
It warned that extra measures may be needed this year.
It is an independent body set up to monitor and advise on budget targets.
For the years up to 2015, it said the Government ought to introduce an extra €2.8 billion in budget measures on top of what is already planned.
Given the very uncertain outlook for growth in Ireland's main trading partners, the Fiscal Advisory Council questioned whether the Government's assumption of real growth of 1.3% of GDP can be achieved this year. It noted that most forecasters now say growth will be less than half that level.
Because of that, the Council said it may be necessary to take further tax or spending measures worth about €400m this year to stay on track for a budget deficit of 8.6% of GDP.
It also said the uncertain conditions reinforce the argument it made in a report last October, when it called for a bigger budget consolidation exercise than that planned by the Government. In an updated version of that plan, the Council calls for an extra €2.8 billion of tax and spending measures, which would total €15.6 billion in adjustments. This compares with the Government's plans which currently total €12.4 billion.
The Council's plan would leave the Government with a budget deficit in 2015 of 1.7%, compared with the Government's target of just under 3%.
''The high degree of uncertainty in the global economy, particularly in the euro zone, means that prospects for Irish exports and domestic demand for the year are now more muted than was the case when the Budget was published,'' the Council stated in its second assessment report.
It warns that the behavioural dynamics - of households, investors and financial institutions - in the ''post bubble'' Irish economy are quite some way from being fully understood at this time.
''The Council is of the view that it would be helpful if the presentation of forecasts were to give greater prominence to uncertainty and include a clear assessment of the risks,'' today's report said.
''This could be done through the use of error bands around forecasts as well as a more detailed assessment of alternative short and medium-term scenarios,'' it added.
