Montgomery County Executive Charles W. Gilchrist announced yesterday he had included a $2.5 million increase in his proposed budget for the year beginning July 1 for day care and other special programs for children.

Of the total, $1.7 million would go to expand the county's day care programs, including the purchasing of four modular units that would be placed on public land and leased to private child care providers.

County officials said they hope to buy 18 modular units during the next six years to lease to day care operators for accommodating 6,000 children.

An additional $650,000 would go to expand day care subsidies to low-income residents. The funds would cover an additional 150 children.

Montgomery County this year is spending $3.6 million on day care services. Gilchrist said he has proposed raising that amount next year to $5.3 million, an increase of almost 50 percent.

After day care, the second largest single expenditure Gilchrist proposed would be $466,500 to staff a new center where children who are abused or sexually assaulted could receive psychiatric and medical help.

Gilchrist spoke at a morning news conference in the former Hungerford Park Elementary School in Rockville, now the Children's Resource Center, which will serve as the county's child care operations headquarters and also house an infant and toddler care wing starting Saturday.

Between 12,000 and 14,000 children are being cared for in county-licensed child care centers and private homes, but many more child care centers are needed because Montgomery County has 65,000 children under the age of 14 whose parents work, county officials said.

"Working families continue to need more centers and day care homes," said Gilchrist.

The county will rent space to day care operators for between $3 and $6 a square foot, compared with up to $15 a square foot on the private market, said Joan Wilson, director of the Children's Resource Center. Wilson said the lower rent would enable day care operators to pay staffers larger salaries and thus attract more qualified personnel.

At the Resource Center, the county will rent space to two private day care operators.

One of them, the Rockville Day Care Association, recently had to move one of its five day care centers out of a public school in Rockville because the school needed room to accommodate more regular students.

Eleanor Northway, executive director of the Rockville Day Care Association, said two more of her group's centers will lose their homes in public school buildings next fall.