Several nonprofit organizations that serve the mentally ill, the homeless and the poor in the Washington area’s largest jurisdiction have formed a united front to lobby the Fairfax County Board of Supervisors to preserve current levels of social services funding, despite pressure from some quarters to ease the burden on taxpayers.

“We recognize that the Board of Supervisors has tough choices ahead of them,” said Amanda Andere of Fairfax Area Christian Emergency Transitional Services. She said several private organizations, including Northern Virginia Family Service, Alternative House, are concerned that the county could cut programs for its most vulnerable people, especially after the county executive issued a list of possible items for the chopping block.

In particular, several nonprofit organizations urged county leaders not to reduce contributions to programs that serve homeless children or to a pool of money known as the “consolidated funding pool,” which nonprofits compete to use through competitive and innovative strategies.

“We are willing to pay more in real estate taxes in order to maintain the quality of life,” said Ann Zuvekas, head of the Fairfax County Alliance for Human Services.

But a taxpayer watchdog organization says that rising taxes are squeezing the middle class out of the area’s wealthiest jurisdiction and that government officials could still trim plenty of fat from the bureaucracy without harming social services.

Arthur Purves, president of the Fairfax County Taxpayers Alliance, said that despite the county’s efforts to style itself as well-run and efficient, its government has lavished its employees with generous salaries, benefits and pensions that residents can ill afford. In the past 12 years, spending on pensions and health care for its staff has more than doubled, Purves said.

“We have Wisconsin here, even though we don’t have collective bargaining,” Purves said.

County officials are well into the process of drawing up a spending plan for the new fiscal year that begins in July. County Executive Anthony H. Griffin has proposed a budget that would leave the current tax rate unchanged, maintain the same contribution to public schools as last year and freeze county employees’ pay for a third consecutive year.

Yet Griffin’s proposed budget, which anticipates rising home values, would still increase the average homeowner’s tax bill by about $111 a year. His proposed budget also left the Board of Supervisors about $30 million to use at its discretion — a sum that now appears to have grown by $4.7 million, thanks to robust holiday sales in December and other favorable trends. It could be returned to taxpayers or used to reduce program cuts or give county employees pay increases.

At the board’s budget committee meeting Tuesday, Kevin H. Bell, chairman of the Human Services Council, urged supervisors to maintain support for critical programs, especially in the face of threatened cuts by Congress.

If the House of Representatives were to prevail with its proposed cut of $1.1 billion, or 15 percent, to Head Start, the county would suffer a loss of $1.1 million, thereby increasing the waiting list of 1,326 children, Bell said in a letter to the board.

Melissa Bondi, campaign director for the Center for Nonprofit Advancement’s and the Nonprofit Roundtable’s regional Think Twice Before You Slice Campaign, said Fairfax’s challenges are perhaps greater than Montgomery County’s, owing to the different levels of state support for human services.

Afterward, board Chairman Sharon S. Bulova (D) said the county would be unlikely to cut social services spending further.

“Fairfax County has consistently done right by the people who need our help, even during the Great Recession,” she said. She said the cuts suggested by Griffin — listed in response to a board member’s query — have been proposed and rejected in previous years when the county’s finances looked worse.

But Purves said county spending is out of control. Since fiscal 2000, the typical Fairfax household’s tax bill has climbed faster than inflation, to $4,901 a year from $2,407.

“The question is, where is it going?” Purves asked. While both the county’s population and workforce have grown about 10 percent in that time, Purves says spending on county salaries has climbed $141 million, or 20 percent. Pension funding has risen $99 million, or 146 percent, and spending on employee health care has jumped $138 million, or 173 percent, Purves said.

Plus, the extent of the spending increase has also been deftly camouflaged by the county’s use of a real estate tax rate that no longer includes the amount spent on stormwater and sewage, Purves said. That tax adds an extra 1.5 cents per $100 of assessed value, making the property tax rate 1.105 per $100.

“They’re playing a shell game with you and me,” Purves said.

Supervisor Pat S. Herrity (R-Springfield) said that despite all the talk of reductions, the county has trimmed only about half a percent from county spending since 2008 and can afford to trim more. He said he will not support a tax rate above $1.065, which would mean that there would be no effective tax increase for residents, and further spending cuts.

“I’m not saying they’re coming from social services, but they’ve got to come from somewhere,” Herrity said.