Chancellor Gordon Brown found his fiscal targets back in the firing line today after his forecasts for the next year were again dubbed optimistic.
He stuck by earlier growth forecasts but found economists questioning whether his hopes of a #10 billion improvement in the nation's finances can be met during the forthcoming financial year.
With the economic cycle due to end in 2006, a planned reduction in the budget deficit from #16 billion in 2004/05 to #6 billion in the following year will be crucial to the Chancellor's hopes of meeting his golden rule.
Mr Brown is confident he can meet the rule - to borrow only to invest on average over the economic cycle - with an overall margin of #6 billion, narrower than the #8 billion he forecast at the Pre-Budget report in December.
He has proved experts wrong in the past and pointed out today that GDP in 2004 had been better than most City expectations at 3.1%.
However, economists believe the key golden-rule measure will be tighter to call, as Mr Brown has pinned his hopes on GDP growth of between 3% and 3.5% in 2005 and between 2.5% and 3% in 2006. On average, the City is looking for 2.6% this year and 2.3% in the following year.
Peter Spencer, chief economic adviser to Ernst & Young's Item Club, said: "There has been quite a marked deterioration in the Chancellor's forecast of the deficit for this year and it's really touch and go on his golden rule.
"The #16 billion for this year looks credible and in line with our forecasts. But it's very hard to see how he can then move that down to #6 billion for next year.
"That is 1% of GDP and it will take an extremely strong economy to do that. I have my doubts about the chances of this being the case."
Andrij Halushka, economist at the Centre for Economics and Business Research, said: "We think the Chancellor's forecast for economic growth in the UK is on the optimistic side. We think it's more likely that the outcome will be closer to the low side of his forecast and in fact undershoots it rather substantially."