Mayor Bloomberg could be overestimating the economic woes facing the city and underestimating future tax revenues by more than $1 billion, according to a new report by the Independent Budget Office.

Mr. Bloomberg and the City Council speaker, Christine Quinn, have warned that 2010 could be especially hard on the city’s finances. The IBO’s new report predicts a loss of 59,400 jobs between now and the middle of 2009 and a recession as the city’s financial industry deals with fallout from the subprime mortgage crisis. But the report predicts the budget will balance out thanks to fiscal surpluses in previous years, as well as tax revenues that are $1.2 billion higher than those projected by the mayor’s office.

The chief of staff for the IBO, Douglas Turetsky, described the city’s short-term fiscal outlook as “surprisingly positive” given the worsening economic climate. He cautioned that if current projections for the 2011 and 2012 budgets are accurate, however, the city will have a “fairly significant problem to deal with,” as rising costs are expected to eclipse tax revenues.

The report predicts a budget gap of $3.3 billion in 2011 and about $4.3 billion in 2012, and warns that the shortfall could be worse if labor settlements boost the city’s expenses or temporary property tax breaks in the current budget are kept in future years. The gap is less severe than projections from the mayor’s office, which see a shortfall of $4.9 billion in 2011 and $4.4 billion in 2012.