The number of homeless families in the city is on the rise even as spending on homeless prevention programs and shelters increases, according to a new report released by the city’s Independent Budget Office.

There were 8,848 homeless families in shelter in the city’s most recent fiscal year, which ended July 1, up from 8,712 in 2004, the report found. The number of single adults in shelter has gone down by 1,456 since 2004, to 6,976 from 8,432.

The report indicates that Mayor Bloomberg’s five-year plan to reduce homelessness in the city by two-thirds by 2009 may be failing. It says that, while efforts to prevent homelessness have expanded, the goal of reducing the number of families and single adults in emergency shelter has not been met.

“We aren’t going far enough, and the overall numbers prove it,” a City Council member of Brooklyn who requested that the city’s Independent Budget Office conduct the study, Bill de Blasio, said yesterday outside City Hall. He said the city needs to begin an “all-out effort” to meet Mr. Bloomberg’s original goal. “No one wants to go to shelters. Everyone wants decent affordable housing for their families,” he said.

Spending on homelessness prevention is on the rise, with $191.2 million spent on prevention programs in 2007, up from $160.6 million in 2004. Spending on homeless shelters also has grown, to $603.5 million from $563.4 million in 2004.

Mr. Bloomberg said yesterday that the city is committed to reducing homelessness and that unless tough goals are set, “you are never going to do it.” He said he thought the economic slowdown, housing crisis, and a more comfortable shelter system could be contributing to the rising numbers.

“Without our efforts, I think it probably would be a lot worse,” he said. “Can we reduce it? I can tell you that every day we are continuing to try.”