Montgomery County agencies say that if a tax-cutting charter amendment passes in November they expect to have to freeze wages, lay off employes, end the Ride-On bus program and defer construction or expansion of 27 parks to stay within their budget for 1980.

Facing the prospect of reducing services by 10 percent if the charter amendment passes, budget officers have been searching for programs that could be curtailed without violating state or federal laws or debt payment requirements.

With a growing number of civic organizations endorsing the charter amendment to roll back property taxes, the government agencies have begun preparing written plans for cuts in services that budget director John Short Friday said would be "substantial, no doubt about it."

Friday, the Allied Civic Group, a federation of civic associations across the county, added its support to the TRIM (Taxpayers Relief in Montgomery) ballot proposition to that of the four chambers of commerce and at least eight candidates for the state legislature and county council who had previously endorsed it.

Meanwhile, opposition to TRIM also continued to mount as the League of Women Voters announced at a press conference that it would fight vigorously to defeat the ballot question. League officials called it a simplistic "cop-out" rather than an informed break on government spending.

"It's like saying, 'all politicians are crooks; therefore I won't vote,' said league action chairman Kathy Ziffer. "If they really wish to save money, this is not the way to go about it."

One argument against TRIM, she said is the legal uncertainly over how much it would chop from the budget.

The Taxpayers League contends that its rollback would apply only to the $2.60 general property tax rate, but County Attorney Richard McKernon told the council that the charter amendment would also cut special taxes for services such as recreation and sewers, which vary across the county.

The Taxpayers League, which proposed TRIM, has said $25 million would be cut, but the county attorney has said that the sum could be as high as $90 million. The budget, without TRIM, is expected to total $561 million. The dispute is not likely to be resolved before election day, and at any rate will have to be settled in court at an additional cost to taxpayers, Ziffer said.

The Taxpayers League referendum, ballot Question E. proposes a rollback in the property tax rate from $2.60 per $100 assessed value to $2.25. Any increase above $2.25 could be approved by six votes of the seven member county council after a public hearing, according to the proposition.

The league declined to take a position on Question D, the county council's own attempt to offset TRIM, which requires that increases in the county's operating budget be no higher than the increase in the cost of living in the metropolitan area.

In a letter to all agencies, Council President Elizabeth Scull asked for projected budget cuts in the event TRIM passes.

The effects of TRIM, if it passes, according to the letter, would be heightened to an expected $21 million deficit this year. The council reduced the property tax rate in June in a pre-election move.

In response, the school board has proposed freezing wages as a method of coming up with half of the minimum of $26 million in cuts that TRIM could force upon the school system. In addition, other savings would be found by reducing the seven-period day to six periods in all schools, increasing average class size by one pupil, and cutting the number of clerical employes, custodians and teachers' aides. Some administrative offices, equipment, personnel and travel also would be eliminated, according to the proposal.

But Superintendent Charles M. Bernardo said in a memo to the Board of Education that the ability to freeze wages is constrained by current teacher union contracts that call for a 5 percent cost of living salary increases. "If the Taxpayers League proposal is adopted and there is no wage freeze agreed to in contract negotiations," he said, "nearly twice as many positions would need to be eliminated from the budget."

The Montgomery County Planning Board in response to Scull's letter, has figured out how to eliminate about $2 million in park development and to defer plans for another $1.4 million in park programs. A total of 27 facilities could be affected in all sections of the county.

"Our program is designed to preserve what we have and hold off on building more tennis courts, bicycle paths, ball fields and recreation centers until such time as the tax base is expanded to pay for what is needed to make the system work," said Planning Board Chairman Royce Hanson.

The reductions will, however, mean a decline in mowing, cleaning and patrolling the recreational facilities, Hanson said.

Budget director Short, who has to come up with about $15 million in reductions from the rest of the government to comply with Scull's request, has not yet devised his cut list. Some of the decreases will come from the county's fire departments.

Short said Friday that some employes would probably be laid off and employes' salaries, miscellaneous grant programs and maintenance on roads and buildings would be likely reduced. In addition, he said, library services would probably be curtailed so that some libraries would be closed or faced reduced hours.

One possibility would be to lay off 750 employes, because of their average salaries of $20,000 each, including fringe benefits, would provide the necessary $15 million savings, he said.

Here is a list of parks the planning board has selected for possible deferral or cutbacks:

Elm Street, Rock Creek, Williard Avenue, Battery Lane and Edgemoor in Bethesda-Chevy Chase; Hillandale, Martin Luther King Jr., Meadowood, Stonegate and Woodlawn in eastern Montgomery; Agricultural History Farm, Stewartown, Blueberry Hill, Gude Drive, Muncaster and Redland in the Gaithersburg area; Greenwood and Olney Square in Olney; Dickerson, John Haines, South Germantown and Little Bennett in the upper county; Harmony Hills in Aspen Hill; Kensington Heights, and Montgomery Hills, Pinecrest and Seven Oaks in Silver Spring.