The leader of an anti-tax group seeking to change Fairfax County's form of government has abandoned hope of having a referendum on the issue this summer and is considering putting the effort on hold until November 1991, when the Board of Supervisors faces reelection.

Frederick T. Dykes, the founder of Citizens for Sensible Taxation, said yesterday that holding the referendum this summer "does not look doable now." Putting the issue on the ballot in November 1991, he said, could cause political problems for the supervisors in their bids to return to office, one of his group's prime objectives.

Dykes conceded temporary defeat after it became clear that petitions his group collected demanding the referendum did not contain enough valid signatures. The registrar concluded that two weeks ago, saying that the group fell 778 signatures short of the 40,589 needed to compel a special referendum. A Circuit Court judge gave Dykes permission to review the petitions and try to prove that some signatures were valid.

"We have had a lot of people working on that, and we came up with 100 to 150 signatures that should have been counted, but not anywhere close to the 800 we needed," Dykes said. "So the options are to hold the referendum this November or the next November."

Dykes declined to say which option he preferred, but said that holding the referendum in 1991 had some advantages.

"We are still collecting signatures and we will file them again and this time we will have a very, very comfortable margin," he said.

One supervisor said the group wants to delay the referendum because it knows the measure will lose.

"I think Mr. Dykes is afraid to put it on the ballot because he will lose on the merits and seriously damage his credibility in endorsing candidates in the 1991 elections," said Supervisor Lilla Richards (D-Dranesville). "I want to have the referendum {this November}, get it over with, and get the discussion back to where it belongs, which is how are we going to pay for transportation improvements."

For more than a year, the group has been shooting for a referendum this summer to change Fairfax's urban county executive form of government to the county manager form. Changing the form of government this summer, the group believed, would force the supervisors to face reelection this fall, a year before their regular terms end.

The point, Dykes has said, was to have a show of force that would persuade state and local officials to enact laws limiting the amount of real estate property tax increases to no more than 5 percent a year.

"It takes a constitutional amendment {to permit the tax limits Dykes wants}, so while they're spinning their wheels trying to get a referendum, they should be down lobbying the General Assembly," said Supervisor Joseph Alexander (D-Lee).

One of the main advantages of a 1991 referendum, Dykes said, would be to force new board elections the following year if voters approve a change in the form of government. That would give the group two opportunities to unseat current board members, he said.

According to some legal experts, that is the fundamental flaw in Dykes's plans. According to an opinion by state Attorney General Mary Sue Terry, the state Constitution prohibits a sitting board from being ousted by a change in the form of government. Dykes disagrees with her interpretation.