The president of the Fairfax County Chamber of Commerce, which has assumed an increasingly important role in county politics, yesterday accused some of Fairfax's supervisors of taking antibusiness positions and making "irrational statements" about development of the county.

"Some members of the Board of Supervisors are treading on a very thin line," chamber President Florence E. Townsend told a luncheon meeting attended by four of the nine supervisors. "I'm not sure of their intention. A lot of it could be speaking without thinking."

What has made chamber officials unhappy are recent votes by the supervisors urging the county's largely autonomous economic development authority to tighten up its policies for approving so-called "tax-free" industrial revenue bonds for businesses that agree to locate in the county. With interest rates at current high levels, companies are increasingly competing for the low-interest bonds, but the supervisors have told the authority that it has been issuing them to freely.

Townsend, a banking executive, disagreed yesterday with the board and warned the supervisors that she is appealing to the chamber's 2,600 members to put pressure on the County Board for a more positive attitude toward business."It's in effect a referendum," Townsend said.

Townsend's comments drew an immediate denial from Supervisor Sandra Duckworth (D-Mt. Vernon), one of the supervisors who supported the votes asking the development authority to tighten its bond policy. She said it was "absolutely untrue" that the board was antibusiness.

"I don't see any basis for this fear," said Duckworth, a chamber member herself, who shared the luncheon dais with Townsend. "They're looking for ulterior motives that are not here . . . They are blowing it out of proportion."

Fairfax Board Chairman John F. Herrity, who sat next to Townsend, also dissented in part. "Every private organization in the county has a right to make its own judgment about any officials of the county . . . I'm not sure I would go that far [and characterize remarks by some supervisors as 'irrational']."

Herrity stressed that business accounts for 25.2 percent of the county's revenues, and said that as recently as last month the supervisors affirmed that economic development was their number one priority. The two other supervisors at the meeting, Marie B. Travesky of Springfield and Joseph Alexandria of the Lee District, left the meeting before Townsend spoke.

Townsend said the chamber's concern goes far beyond the industrial revenue bond issue. "When we have members of the governing body of the county making irrational statements and then these statements are published in The Washington Post, there is a great deal of danger for the continued economic development of the county" she said.

"If I were an executive of a company considering moving to Fairfax, and I read those statements in The Washington Post, I would have second thoughts about relocating there."

Townsend said the county "can never go back to the days of the early 1970s," when the previously dormant chamber helped oust then board chairman Jean R. Packard, who had led what many business leaders considered an antigrowth faction on the County Board.

Since the 1975 campaign, the chamber has grown into a potent political force in Fairfax. It has doubled its membership in the past three years.

But it has done more than add numbers. While the chamber used to be dominated by small-business people, its boardroom now includes officials from most of the big-name corporations that have moved to Fairfax in recent years. Mobil Oil, BDM Corp., Dynalectron Corp., and AT&T Longlines are all represented in the chamber's decision-making hierarchy.

For example, one of the chamber's directors is Charles Gulledge, head of Dynalectron, the worldwide professional services company based in McLean. Gulledge also is chairman of the controversial economic development authority.

In a series of votes two weeks ago, the supervisors urged the authority not to grant its bonds to businesses engaged primarily in politics. The vote was aimed at a decision by the authority last year, when it tentatively approved a $7 million bond for Richard A. Viguerie, the direct-mail wizard who is associated with many causes of the New Right.

Shortly after the Viguerie deal was disclosed, it was revealed that the development authority also approved a $7 million bond that allowed Marlo Furniture Co. to relocate its corporate offices in a large warehouse-showroom off Shirley Highway. The bonds were issued for the facility, which includes a retail sales area, despite a prohibition on use of the bonds for retail establishments. Some of the Fairfax supervisors were also critical of that transaction.