Officials of the Fairfax County Chamber of Commerce, saying that the county's elected officials are "woefully underpaid," have undertaken a study to determine whether county supervisors should get a pay raise and whether their jobs should be full time.

The nine members of the Board of Supervisors are paid $21,589 a year for their part-time positions, more than $15,000 less than part-time council members in Montgomery County and more than $25,000 less than District council members, also part time.

Chamber official William F. Blocher confirmed yesterday that the local business community has taken up the controversial issue and will report its recommendations to the board before the end of the month. However, he declined to comment on how large a raise the chamber might recommend.

Three supervisors said that they would support a move to make their jobs full time.

"In order to devote our full time and attention to [the job], it should be full time," said Supervisor T. Farrell Egge (R-Mount Vernon), who added that the change should be accompanied by a salary in excess of $50,000.

An even more substantial raise was suggested by board Vice Chairman Martha V. Pennino (D-Centreville), who said full-time supervisors should be paid "at least $90,000." But Pennino added that it would be unwise to make the job full time because many professionals would be reluctant to surrender their jobs for full-time county positions.

Pennino said that $50,000 would be a "reasonable" annual salary for part-time supervisors.

Board Chairman John F. Herrity said he could support a modest pay raise for board members, but would "violently oppose" any salary that exceeded $25,000 a year.

"I haven't seen anyone buy good government yet," Herrity said. He harshly denounced those who suggested making the jobs full time, calling the idea a "scam."

"I'm a firm believer in citizen-legislators," he said.

Chamber officials will meet with each supervisor during the next two weeks before making a recommendation, which the board would then have to approve.

Blocher, former president of the chamber and chairman of its Compensation Review Committee, said that the chamber is tackling the issue because of its concern about the recent exodus of county employes -- most in such areas as the county planning staff -- to private industry. He said the chamber was not approached by any supervisor to conduct the pay study.

Any pay raise enacted could not take effect until the new board takes office in January 1988. Most of the supervisors have said they intend to seek reelection.

Sentiment for a pay increase appears to be building among the supervisors. And three supervisors -- Egge, James M. Scott (D-Providence) and Joseph Alexander (D-Lee) -- said they would back a plan to establish their jobs as full time.

"Our efforts are certainly worth more than the compensation being paid now," said Egge, who added that the current pay scale discourages interest in seeking a board seat.

Alexander said pay raises for board members are "long overdue." He said that although he would favor the concept of full-time positions, he doubts there are five votes on the board for that proposal. He suggested a somewhat more modest increase than Egge, saying the supervisors should be paid $30,000 if the job remains part time and from $40,000 to $45,000 if full time.

Scott declined to discuss salary ranges, but said the supervisors "definitely" should be granted full-time status. Noting that the county is "fast approaching becoming the most populous jurisdiction in the region," Scott said the supervisors' pay level "has never kept up with the responsibilities of the job."

Audrey Moore (D-Annandale) said she would support any salary that does not exceed $30,000 a year. She said making the position full time was out of the question.

"There's going to come a time when Fairfax County won't be going through the development boom it is right now," Moore said. "When that happens, these jobs won't take up that much time."

Elaine N. McConnell (R-Springfield) said she favored an annual pay increase of about 5 percent for board members. Nancy K. Falck (R-Dranesville) and Thomas M. Davis III (R-Mason) were noncommittal.

Davis said that his "gut reaction is that it's not the appropriate time to talk about it," saying it "could become a rallying point for others in the county who want pay raises."

Davis' remark was an apparent allusion to Fairfax County teachers, who have claimed in the past their right to pay hikes commensurate to those granted county employes.

John Elligers, research director for the Fairfax County Council of PTAs and an outspoken advocate of pay increases for teachers, endorsed the idea of full-time supervisor positions. "They should pay salaries that will attract and retain professional supervisors, not part-time housewives or people who view it as something to dabble in."