It said the increase was also due to one-off effects in tax law changes that lowered revenues.
The fiscal deficit stood at 732 million levs ($480.5 million) at the end February from 565 million levs in the same period a year ago.
Protests over low living standards and high utility bills toppled a centre-right government in February and an interim administration will now rule until May 12 election.
It has pledged to maintain fiscal prudence needed to avoid pressure on a currency peg to the euro and run a deficit of 1.3 percent of GDP in 2013, from 0.5 percent in 2012, though it redirected some funds within the budget to help the poorest.
Bulgaria has struggled to restart its small and open economy. Troubles in the euro zone its key trading partner have only allowed it to grow by a relatively meagre 0.8-1.7 percent in the past two years.
The country operates under a currency board regime which curtails significantly its central bank operations, making prudent fiscal policy its key tool to maintain macroeconomic stability.
Spending in January and February was 7.4 percent higher than the same period from a year ago at 4.5 billion levs, finance ministry data showed, while revenues came in 4 percent higher at 3.8 billion.
The fiscal reserve, which the country is obliged to keep under its currency board regime, stood at 3.9 billion levs, down from 4.1 billion in January.