The chairman of the commission that proposed building a new government center in Fairfax County expressed concern yesterday that county officials may be committing themselves to a plan that stresses cost savings and ignores quality.

"The board shouldn't just rush to make a decision on this," warned Michael S. Horwatt, a Fairfax attorney who chaired the commission that recommended in 1978 that the county government move out of Fairfax City.

Officials may be reserving too little land to build an attractive, accessible complex that supports all of the government's needs, leaves room for expansion and becomes the focal point for county activities, Horwatt said in an interview.

He said that was the kind of complex envisioned by his commission, which viewed the government complex as the primary center in the rapidly developing corridor that includes the 180-store Fair Oaks Mall and numerous high-rise office buildings.

"I have a real fear that the county won't match that, that they will weaken the standard rather than strengthen it," Horwatt said.

Fairfax Board Chairman John F. Herrity denied Horwatt's suggestion that the board was moving too fast, but he acknowledged that costs were an important consideration.

"My concept of a government building is that it not be one of the eight wonders of the world," he said yesterday. "It doesn't have to be an architectural marvel, but an attractive structure that will govern this county effectively."

Horwatt said he was "elated that the board has recognized the need for a county center and that it's going to go in the Fairfax Center area. On the other hand, I am concerned that we don't surrender our future on that site."

But Horwatt said that he and other members of his commission were alarmed that many supervisors were ready to support a complex that, much like the county's Massey Building high-rise, might be overcrowded from the day it opens.

Horwatt's comments came a day after the Board of Supervisors unanimously endorsed a proposal to seek a developer to jointly build the center with the county government in return for up to 146 acres valued at between $50 million and $70 million. The board reserved a decision on whether to reserve 70 or 100 acres at the site for construction of the government offices.

The new county offices are to be built on part of a 183-acre county-owned tract near Rte. I-66 and Rte. 50, south of Fair Oaks Mall. County Executive J. Hamilton Lambert has recommended that the leftover land from that tract, plus an additional 33 acres of vacant public land at I-66 and West Ox Road, be offered to developers in return for building the new government offices.

Horwatt applauded the joint venture concept as an "imaginative" way to finance it.

Another concern of commission members, Horwatt said, was the opposition of supervisors, including Herrity, to financing at least a portion of the project through a bond issue.

Horwatt said he also was dismayed by what he said was the board's apparent willingness to dismiss the designs for the proposed government center, which the county paid in excess of $200,000 to elicit from firms around the country two years ago.

Herrity has said he would be satisfied with a new government building that resembles the new Fairfax Courthouse in Fairfax City.

Jean R. Packard, another member of Horwatt's commission and Herrity's predecessor on the board, voiced criticism of the board's actions. "They don't seem to be concerned about what the citizens want," she said. "The whole thing seems to be hinged on saving a few bucks. They did the same thing when they built the Massey Building."

The joint venture plan was hailed as "a super idea" by James P. Popino, president of the Fairfax County Chamber of Commerce. He said, however, that chamber members have some of the same concerns posed by Horwatt and that a chamber committee has been appointed to monitor the government center issue.