Unless they choose to drastically reduce the number of children on their rolls, hundreds of Fairfax County home day-care providers may soon be forced to submit to a complicated, costly county permitting process to stay in business.

Fairfax officials are proposing the measure to try to keep home day-care centers from kicking out thousands of kids in the wake of a state permitting change, but some worry that the new local rules could do just the opposite in an area where parents already face a shortage of child care slots.

At issue is a discrepancy between the number of children the state allows in home day-cares and the number permitted under Fairfax’s zoning ordinance — a problem that came into sharp focus this summer after the Virginia Department of Social Services added a seemingly small requirement for state home day-care licenses.

State licenses allow for up to 12 children per day care, while Fairfax allows only seven in single-family homes, or 10 with a special review and permit. Because county officials do not typically verify whether day-cares abide by the local limits unless neighbors complain, many providers have been following the state’s more generous guidelines.

But under the new state requirement, which took effect July 1, home day-cares applying for Virginia licenses must complete a form saying they are in compliance with county zoning regulations.

If Fairfax were to enforce its existing limits, some day-cares would be forced to cut their enrollments by more than 40 percent. The prospect has alarmed parents and providers alike.

After months of debate over how to deal with the problem, the county now has a formal proposal: raise its special-permit limit to 12 — the same number allowed under state regulations — but leave the limits as they are for providers who don’t want to go through a second, local review.

Providers with more kids than they are currently allowed would be left with two choices: cut their rolls or go through the county zoning review. (The state’s review focuses more on child safety issues.)

The proposal was discussed during a Board of Supervisors committee meeting Tuesday.

According to the county, there are about 500 state-licensed home day-cares in Fairfax. Most of them — nearly 400 — have Virginia licenses for 12 children, and of those only a handful have successfully finished a county permitting process that currently grants permission for 10. That means the vast majority are allowed only seven but probably have several more, and it means hundreds of providers could soon be lining up for a county permit.

While they most wanted a solution that would give them an option for keeping 12 kids, many providers had hoped that the county would go one step further and increase the number of children allowed without a county review. At a packed town hall meeting this summer, they told horror stories that they’d heard from colleagues who have tried for a special permit — how the application and requirements are so confusing that some just gave up; how the fee alone is $1,100; and how some expended months of effort only to be denied a permit because a single neighbor showed up at their public hearing before the zoning board to complain about the extra traffic.

“I think for a lot of people it might be too much,” Susan Gallier, who has a home day-care in Burke, said Tuesday. “I’m planning to do it, but I think a lot of people won’t.”

The county may reduce the cost of a permit, and it is working to simplify the application process, said Leslie Johnson, Fairfax’s zoning administrator.

The Board of Supervisors will vote on the proposal in the coming months. Most board members have said they think it strikes the right balance between keeping home day-cares in business and protecting neighbors, but Supervisor Pat Herrity (R-Springfield) disagrees.

He said that like providers, he wanted the no-permit limit raised, too.

“This means more regulation, more forms and more fees,” he said. “I think we could see our supply of child care reduced, and I think we could see more people choosing to operate unlicensed.”