Mayor Bloomberg’s plan to reduce the city’s homeless population is falling short of its targets, a report released yesterday by the nonprofit Coalition for the Homeless asserts.

The report found that the number of New Yorkers entering the shelter system spiked by 11.1% last year, and the number of homeless families and homeless children in the city increased by 17.6% and 18.1%, respectively.

The executive director of the coalition, Mary Brosnahan, said that halfway through the mayor’s five-year plan to slash homelessness by two thirds, a “midpoint correction” is needed because the city’s own numbers show that the homeless shelter count is going up.

She said New Yorkers are “not going to tolerate continued arrogance in the face of a failed program.”

“When something is implemented and it’s gone this wrong, what we need is for Mayor Bloomberg to step up, admit that a mistake has been made, and take correction action immediately,” Ms. Brosnahan said.

A spokeswoman for the Department of Homeless Services, Tanya Valle-Batista, noted that the census for single adults has been on the decline and said the city recently announced that it would expand its homeless prevention program.

“As the coalition is well aware, DHS has recently moved to expand prevention services and is planning adjustments to our rental assistance program to reverse these troubling trends,” Ms. Valle-Batista said. “While the rest of the nonprofit community is working with the city to address these issues, the coalition continues its opportunistic efforts to generate headlines.”

She added, “As a result of this administration’s reforms, the family intake center is finally able to accommodate surges humanely and effectively as we work to turn the numbers around.”

Homeless advocates have long criticized the city’s Housing Stability Plus program, a rental subsidy program the city established after the federal Section 8 voucher program was cut.

While they laud Mr. Bloomberg’s goal, they say Housing Stability Plus was set up for failure because it cuts rental subsidies by 20% a year and is available only to those on public assistance. As a result, a senior policy analyst at the coalition, Patrick Markee, said, the program acts as a disincentive for those on the brink of homelessness to get jobs.

Housing Stability Plus is the largest program of its kind, and some homeless services officials note that the administration is criticized whether the number of people coming into the shelter system is up or down.

One of the main factors driving the increased homeless population is the strong economy, which has pushed rents higher — something the administration has little control over. Simultaneously, incomes for low-income residents have been down, squeezing the poor out of the market, coalition officials said.

The city, which would need approval in Albany for changes to its rent-subsidy program, recognizes couples without children as families — a fact that is driving up the homeless family statistic.