A $10-a-month parking fee at Harry Diamond Laboratories in Adelphi has sent employes swarming onto surrounding residential streets in search of free spaces.

Neighbors of the Army weapons research facility are angry, so angry, according to some Diamond employes, that radio antennas have been snapped off, glass spread under one car and notes left on several windshields.

Col. William Benoit, commanding officer of the 1,300-employe facility, said an anonymous caller threatened more serious vandalism if workers continue to park their cars on neighborhood streets.

The Hillendale Gardens Citizens Council has written letters of protest to the laboratory and to Rep. Gladys Noon Spellman (D-Md.) complaining that the government is not living up to a promise to provide adequate employe parking.

The promise was made in 1968 to reassure residents who opposed construction of the facility, Benoit said.

"We do have ample parking," he said. "A lot of it is going unused because people don't want to pay to park."

The $10 fee was imposed Nov. 1, after President Carter ordered federal employes to begin paying to park.

Benoit said bus service to the Army faciity is inadequate and many employes commute from distant locations.

"We have people coming from Springfield, from Manassas, from Vienna, Bowie, Baltimore, they come from all directions," he said. "It's hard to get car pools together."

"The (pay-to-park) policy was designed for urban areas, where they have public transportation," Benoit said. "It is just inappropriate here. I feel it is misapplied."

Teresa Chillemi, a Vienna resident who works in the laboratory's purchasing department, agreed. "There are no bus lines for me to take from Vienna," she said, adding that the situation is no better for most Prince George's County residents.

Benoit filed one unsuccessful appeal with the Secretary of Defense and said he will try again.

Spellman has gone to bat for the laboratory by writing a letter to President Carter asking that the employes be exempted from the pay-to-park program.

"I don't think the chances (of winning an exemption) are overwhelming," said one Spellman aide.

"It wouldn't be so bad if they weren't so inconsiderate," said one homeowner, referring to the Diamond employes. "If they weren't blocking people in their driveways and parking so close to fire hydrants, I don't think people would be so concerned."

"If a person leaves his house in the morning and comes back before five, he won't find a place to park his car," said George Miller, co-chairman of the Hillandale Gardens Citizens Council. "It's dangerous. People have a difficult time getting out of their driveways because they can't see the traffic."

Chillemi said taxpayers are the losers in the battle, pointing to an internal memo that places the cost of the first two months of the pay-to-park program at $20,750 more than the program brought in.

Benoit confirmed that figure, saying it includes start-up expenses. Eventually, costs could be brought down by contracting with a firm that would manage the parking lot, he said.

Expenses will be paid from a budget "that is supposed to be devoted to weapons systems" Benoit said. "That's not a complaint, that's a fact."