Fairfax County's business community lobbied with unusual force yesterday to defeat a proposal that would have ejected major landowners from the Fairfax Economic Development Authority.

Supervisor Audrey Moore of Annandale proposed that executives of commercial real estate companies be excluded from the powerful seven-member authority, which helps arrange low-interest loans for businesses seeking to move to or expand in the county. She argued that such executives might profit or appear to profit by encouraging certain business relocations or by learning of other companies' plans. Her proposal was defeated 7-to-1 with one abstention.

"She's really gone beyond the pale this time," said Philip Reilly, president of the Fairfax Chamber of Commerce, who attended the session along with several authority members. "This business of assuming people are hiding things simply because of the business they're involved in is an insult, and we've had quite enough of these kinds of insults."

The supervisors' rancorous discussion on the authority highlighted a day of unusually bitter debate among the nine supervisors on the role of developers should have in the fast-growing county.

The board received a consultant's report that said county taxes have risen faster than they otherwise would have because of rapid residential growth. The supervisors debated for more than two hours the conclusions and policy implications of that study, and ended by taking no action.

The supervisors also learned that county taxpayers will have to pay $9.3 million to complete roads, sidewalks and other public improvements on which subdivision developers defaulted on in 1981. "That's where the board has really fallen down," said Mason District Supervisor Thomas M. Davis III. "That's a disgrace."

The board approved hiring another consultant to study how to prevent such defaults in the future--and then held another rancorous debate on whether to allow the Northern Virginia Builders Association to help oversee the consultant's work, as the builders had demanded. The board eventually compromised by placing one builder and one consumer representative on the oversight committee as nonvoting members.

Moore's proposal to keep landowners off the Economic Development Authority, which coincided with the end of James W. Todd's term, touched off the most emotional debate. Todd is president of the eastern division of the Mobil Land Development Corp., which oversees the marketing of several hundred acres of industrially zoned land in Reston as well as projects in Arlington and Atlanta.

Moore said her policy was not directed at Todd and did not imply any acts of impropriety. But she said the presence on the authority of Todd and other landowner representatives could create a "public perception" of conflict.

"Information available to members of the Economic Development Authority cannot help but be of assistance to developers of commercial property," Moore said. "This is not fair to other owners of competing commercial land."

Todd said in an interview that said there is no conflict of interest because the county is as interested in promoting economic development in Reston as is his firm. He added: "This is one of those happy situations where the county, the Economic Development Authority and a major landholder all have synonomous policies."

The board agreed, with Moore voting against Todd and James M. Scott, who represents the Providence District, abstaining. "I personally offer an apology to each and every member of the Economic Development Authority," said Dranesville Supervisor Nancy Falck when the debate was over.