The document was passed by Ukraine's 450-seat parliament on Friday.
"The president has signed the budget," Oleksandr Shlapak said, adding that he did so to avert problems with covering basic social payments in January.
Shlapak cited Yushchenko as saying that the document, one of the most problematic in a decade, had a number of shortcomings. "GDP growth fixed for 2009 at 0.4% is more desirable rather than realistic," he said.
For this reason, the official expressed doubt about the 20 billion hryvnias ($2.59 billion) in budget revenues. "This is more virtual than realistic," he said.
Shlapak also said domestic borrowings worth 70 billion hryvnias ($9.3 billion) were very unlikely.
The inflation projection is 9.5% and the budget is forecast to run a deficit of 2.96% of GDP, despite protests from the president.
The new budget law also stipulates that all wage taxes be replaced by a unified social tax.
