Two Fairfax County supervisors, seeking to stem the exodus of county employes to the local development industry and to avert potential conflicts of interest, said yesterday they would propose an ethics law next week that would sharply curtail former employes' contact with the government.

Saying that such a law was long overdue, Supervisor Audrey Moore (D-Annandale) and Board Vice Chairman Martha V. Pennino (D-Centreville) said in separate interviews that Fairfax should move promptly to close the revolving door between the county and developers.

Under Moore's proposal, a Fairfax employe would be prohibited for at least one year from having any contact with the government on programs that the employe had worked on.

Moore said it appears that Fairfax would need authorization from the Virginia General Assembly to adopt such a law. She said she would urge the county board at its meeting on Monday to ask the legislature for that authorization, and that the request could be made in time for the legislature's special session in September.

"We have let this go for far too long," Moore said. The departure of county planning staff members to jobs with local developers and with consultants hired by those developers "creates the potential for abuses [and] sends a bad message to everyone," she added.

"We've set up a system where this could happen," Pennino said of the resignations. "We've sat around on our hands. None of us has moved to do anything, which is very stupid."

The proposal by Moore and Pennino was denounced by Fairfax Board Chairman John F. Herrity, who said the issue should be studied but that forcing a decision by as early as next week would be an "hysterical" reaction to a newspaper article.

The Washington Post reported Sunday that a few dozen Fairfax planning and development employes have left the county government during the 1980s for more lucrative jobs with local development-related firms. In some cases, the article said, former county employes now with developers were working on projects on which they had played a key role while in the government.

"Why does a deliberative body have to have an emotional orgasm because somebody writes a story?" Herrity asked yesterday. "I don't favor a hysterical rush into this issue."

"It's obvious that, politically, we have to look at this," Herrity added, saying that he would propose on Monday that the board ask the county's lawyers to review the issue and to recommend what steps the county can take. "I think it's important that we understand what we're doing before we do it. I don't like emotional government."

Pennino predicted that the law's chief effect would be to shut off the flow of county employes to the development industry. She said developers would be reluctant to hire Fairfax staff members if those employes are prevented from involving themselves in sensitive projects needing county planning, zoning and other building-relating approvals.

"I think they'd [the developers] just stop hiring them," Pennino said.

Supervisors James M. Scott (D-Providence) and Joseph Alexander (D-Lee) said they probably would support a motion next week to seek legislative approval for the new ethics provision, placing all four Democrats on the board behind the measure.

The Fairfax board opposed suggestions in past years that it adopt such an ordinance, contending that it lacked the authority from the state to do so. Similar laws are in effect in area jurisdictions, including the District and Montgomery and Prince George's counties.

Moore and Pennino said there was no reason the board could not seek legislative action during the General Assembly's special session in September, when the legislature is scheduled to take up statewide transportation issues.

Herrity, however, said the county should wait until the General Assembly meets next year.

"There's no way we can get it before the legislature in September," Herrity said. "The legislature doesn't meet again [after that] until January [of 1987]. What the hell's the hurry?"