A new report says as many as 40 libraries could be closed, with many others forced to scale back their hours as part of Mayor Michael Bloomberg's proposed budget cuts.

The report, from the non-partisan Independent Budget Office, says the mayor's preliminary budget reduces library subsidies by 22 percent.

Cuts would fall hardest on Brooklyn, which the City Council estimates would lose 16 libraries.

Council members estimate Queens would lose 14 branches, and the New York Public Library system, which covers the other three boroughs, would shutter 10.

The mayor's office says libraries must get less funding like every other part of government because of drastic cuts in state and federal aid.

The report cautions this is just a preliminary budget, and in previous years proposed library cuts have been restored in the final budget.