Northern Virginia Rep. Stanford Parris, capitalizing on his position on a key housing committee and the Reagan administration's lack of enthusiasm for subsidized housing, has blocked a $3 million public housing project that a Fairfax County housing agency had been planning for three years.

The assistant secretary for housing, responding to a barrage of telephone calls from the Republican congressman's office and a spirited letter from Parris himself, last month took the unusual step of ordering his Washington area office to clear every step of the project with him. Since the developer's option to purchase the land expired last week, the delay effectively has derailed the proposed 30-home development.

"It's not very often you turn down a $3.5 million gift, but then, beware of those bearing gifts," Parris said during a budget markup session in May. Parris said this week he hopes his continued opposition to the project -- along with a cut in the subsidized housing funds in the 1982 federal budget he helped shape -- will convince U.S. officials to send the money elsewhere once and for all.

"He Parris has been very, very persistent," said Jeanne Smith, HUD assistant for congressional relations. "As a result of his persistence, we are where we are today."

Parris' success reflects not only his persistence, but the Reagan administration's reluctance to force public housing into resistant suburban neighborhoods.

"This is one reason the Reagan administration is trying to move in the direction of more local control over how these funds are spent," Smith said. The administration proposed funding 175,000 public housing units in 1982, down from this year's 280,000. Congress eventually authorized only 153,000.

The case also demonstrates the difficulty of providing shelter for poor families in Fairfax, where subsidized apartments often are opposed as incompatible with existing homes and single-family houses are attacked as too expensive. The single-family houses in Coventry, the project that Parris has opposed, would cost the government at least $85,000 each.

There are currently 500 public housing units in the county, which has a population of 596,900.

The Fairfax County Redevelopment and Housing Authority, as determined to develop as Parris is to prevent development, last week purchased the 11 1/2-acre site in West Springfield for $445,000 when the developer's option expired. Although federal funds for future development are very much in doubt and although they would have to begin the cumbersome development process all over again, housing officials still hope to build something on the site, at Hillside and Center roads.

"We don't take this as a defeat," said housing authority spokeswoman Deirdre Coyne. "It may take a little more time, but we'll do it."

The land purchase prompted Parris to fire off another letter last week, this time to Housing and Urban Development Secretary Samuel R. Pierce Jr.

"As a member of the committee of Banking, Finance and Urban Affairs, I continue to oppose this project as inefficient, a poor selection of site and a true example of government extravagance," Parris wrote on Sept. 18.

And John F. Herrity, chairman of the Fairfax Board of Supervisors and another Coventry opponent, has summoned housing authority officials to the board's Monday meeting to explain the land purchase. Although the authority is independent, it depends on the supervisors for much of its budget.

Parris said he objects to the West Springfield site because of neighborhood opposition, but even more because of the projected cost of the houses. The authority says it is willing to spend $85,000 for each house on the site and a developer proposed charging more, $102,000 per house. Because of Parris' opposition the authority and the developer never negotiated a final price.

"I think subsidized housing does not necessarily have to be the classiest housing in the community," Parris said. "I think we should be building acceptable shelter, not the equivalent of what the president of a bank would own."

Coyne said land prices and building costs are expensive in Fairfax, no matter who the developer. "Fairfax County is saying,' we do want to provide housing for low- and moderate-income families,' " Coyne said. "Well, we can't build cheap, shoddy stuff, and if we could, we wouldn't."

Coventry originally was conceived as a 50 town house turnkey project, with a private developer buying the land, building the houses and then turning them over to the housing authority for sale to low- and moderate-income families. Partly due to mistakes made by the housing authority -- allowing a change from town house to single family without re-advertising, for instance -- and to the zeal with which opponents found those mistakes, developer Ray W. Lotto has spent more than two years and $40,000 on the project.

"As far as I'm concerned, the community managed to delay it long enough that time just ran out," Lotto said yesterday. Lotto, who said he believed no public housing design would satisfy Fairfax County residents, has built more than a dozen federally subsidized projects, mostly in Seattle and Portland.

In those communities, he said, "the people usually compete for these funds, believe it or not."