The homeless population in New York City has jumped sharply over the last year, causing a record number of people to enter the shelter system. The increase has forced the Bloomberg administration to open nine more shelters in just the last two months — sometimes with only a few weeks’ notice to surrounding neighborhoods.

The administration said the increase stemmed in part from the end of the city’s main rent-subsidy program for homeless families. But the new shelters — five in the Bronx, two in Manhattan and two in Brooklyn — have provoked criticism from local officials who say they were blindsided by the decisions to open them.

The city, for example, relied upon its emergency authority to turn two residential buildings on 95th Street on the Upper West Side of Manhattan into shelters that will eventually house about 200 adult couples, officials said. The buildings had recently been used as illegal hotels before they were shut down, and they still have some long-term tenants.

The city’s Department of Homeless Services told the community board about its plan in mid-July, only two weeks before people began moving in.