Richard A. Viguerie, the direct mail champion of conservative causes and the free enterprise system, has found a government program that should save him millions of dollars.

Officials of the Fairfax County Economic Development Authority said yesterday that the agency has agreed to help Viguerie finance a new $7 million office building through a loan transaction that will be exempt from U.S. income taxes.

The action should lower considerably -- perhaps by as much as half -- the cost Viguerie will face in financing a new home for his direct mail operations, currently located in leased office buildings near Tysons Corner in the county.

"There were misgivings" about the proposal, said David A. Edwards, executive director of the public authority, which frequently has used tax-free financing schemes to help attract industry to the suburban county. "Some of the (authority's) commissioners were not terribly happy, but they went along," Edwards said.

Edwards said the authority approved the Viguerie application because it met all the criteria for getting the special loan status.

Officials of the development authority declined to disclose details about Viguerie's highly touted, but closely guarded direct mail operations.

Using highly refined mailing lists of people sympathetic to conservative causes and polished letters of appeal, Viguerie has raised millions of dollars in the last 16 years. He gained much national attention in 1976 when he raised more than $7 million for George Wallace's presidential campaign, becoming Wallace's leading fundraiser.

Before that he had raised millions of dollars for the National Rifle Association and other conservative groups. His methods have proved controversial and have repeatedly brought him into conflict.

In 1977, when Virginia Democrat Henry E. Howell lost his race for governor to Republican John N. Dalton, he blamed Dalton's direct mail campaign for his defeat. "It was a victory for Viguerie," Howell complained the morning after the election.

Viguerie himself has declined to discuss specifics of his operation, but in 1978 he said that in the previous year he had mailed about 75 million letters -- about 50 million of them political -- from his Northern Virgina offices.

Viguerie could not be reached yesterday but his top aide, James G. Aldige III, said the firm now employs about 75 to 100 persons at its Leesburg Pike offices. Aldige said the new building would be five stories high and contain about 100,000 square feet of office space. He said industrial zoning for the site, located on Rte. 123 in Oakton has not yet been obtained.

The $7 million loan actually would come from a bank or another lending institution. But under a "resolution of inducement" approved by the Fairfax authority's commissioners, the loan will have gilt-edged status, freeing the lender from any federal income taxes on the interest it earns on the transaction.

That should enable the lender to make the loan to Viguerie at a rate well below what it would charge on a taxable loan. For some banks such loans are highly prized. United Virginia Bank, for example, has loaned more than $100 million in Virginia to finance such projects, according to a bank official.

Earle C. Williams, who at the time was chairman of the seven-commissioner development board said there were no dissenting votes on the application -- the largest ever approved by the authority.

Commissioner John E. Lynch Virguerie, "met all the criteria. I voted yes . . . I might not be a cheerleader for some of the causes the (Viguerie's operation) espouse, but if they apply under the state statue and are a good employer, I don't see any problem."

How much Viguerie will save will not be known until his company's loan transaction is completed.

George W. Stephenson, president of Stephenson Inc., a printing company that is moving from the District of Columbia to Fairfax next month, said his firm will save "an easy million dollars" on his tax exempt $2.8 million loan, which was recommended by the authority and granted by United Virginia Bank. Stephenson said that he would have had to pay 11 1/2 percent for his 1978 loan, but with the industrial development authority's approval he ended up paying "less than 8 percent."

According to Joseph B. Murden, executive vice president of United Virginia Bank's Vienna headquarters, industrial development loans at the present time are being granted at a floating rate of 65-to-75 percent of the prime rate. That would put the interest for such loans at about 8 percent A conventional loan could cost the borrower an interest rate of about 13 percent.

Tax free industrial development financing has been heavily used in the Sun Belt states to attract industry, often at the expense of states in the industrially declining Northeast. But in recent years, all regions of the country are pursuing vigorous industrial development programs built around the low-interest loans.

The rationale for the loans is that while they cost the U.S. government taxes, they create jobs and strenghthen local economies.

While industrial development loans once were supposed to go to companies that cannot get conventional financing, an analyst for the Congressional Budget Office said a study shows that "many of the projects would have gone forward with conventional financing."

The total amount of such loans in 1979 was put at $7 billion by the office's still-unreleased study, double the 1978 figure. It estimates that the losses in U.S. income taxes for fiscal 1981 will amount to at least $1 billion.

According to Edwards of the Fairfax authority, Viguerie came to the agency seeking help to build a new headquarters.

As for the political implications, Edwards said. "It was felt they (the Viguerie company) were not revolutionary. It was not as extreme as the Ku Klux Klan. It was in the realm of established political philosophy."