The Federal Communications Commission has postponed for several months any consideration of moving its headquaters and 1,700 employes from downtown Washington to two high-rises in Rosslyn.

In a rebuff to FCC Chairman Charles Ferris and top staff officials who have pushed for the move for nearly a year, Ferris' fellow commission members complained at a meeting last week that they had been "kept in the dark" about the proposal. The commissioners accused Ferris and the staff of trying to ram the plan through without adequately exploring the possibility of other office space in downtown Washington.

Crucial support for the Rosslyn move from the union that represents most Fcc workers also appears in doubt. The National Treasury Employees Union had lobbied extensively in an effort to help the FCC get its own leasing power from Congress and thus make the move to Rosslyn.

After last, week's FCC meeting, however, union president Ed DeVaughn said, "Our people would clearly like to remain in the District." DeVaughn said the union originally had supported the move because top FCC officials had told union members that "we'd end up under the aegis of . . . (the General Services Administration, which finds office space for most federal agencies), and they'd put us out in some place like Rockville or Tysons Corner."

Thomas Campbell, the FCC official who directed the agency's successful year-long drive to obtain its own leasing power, bypassing GSA, said this week he is not surprised at the union's statement. "In absolute terms we'd all like to remain in the District," Campbell said.

The seven-member commission voted to defer the issue until the Reagan administration takes office and until the new Congress has a chance to consider the proposal.

Several congressmen have written the FCC in recent weeks, including Sens. Berry Goldwater (R-Ariz.) and Bob Packwood (R-Ore.) and Rep. John Dingell (D-Mich.), "expressing deep concern" about the proposed move or asking that controversial decisions be delayed, Commissioner Abbott Washburn said at last week's FCC meeting.

In addition, Washburn said, the new administration is expected to appoint its own FCC chairman, replacing Ferris, and will be appointing two new commission members in the coming year, which could change the way the commission votes on the issue.

The new administration and new Congress "should have a say in this decision and not have a fait accompli dumped in their laps in these final weeks," Washburn said.

Although the FCC staff has been working intensively on a move to Rosslyn for nearly a year, at the behest of Ferris, the commission itself never has approved the move and had not discussed the propsal formally until last month, when the staff briefed commissioners on the issue. One commissioner complained at last week's meeting that he had first learned of the plan "from the press."

At the meeting last week, Ferris and Campbell both tried to force the issue, claiming that if the commission didn't immediately approve the leasing of office space in Rosslyn's new Twin Towers, the deal would fall through and it would cost the federal government $9 million.

The $9 million, Ferris and Campbell say, would be the amount saved by moving from Washington's highrent district around Connecticut Avenue NW to Rossyln. Most FCC employes now work in several leased office buildings near Connecticut Avenue and M Street NW. Under the proposed move, the Fcc would rent 22 stories in the 30-story Twin Towers now under construction near the Key Bridge in Arlington.

The FCC has been negotiating to pay less than $17 a square foot for space in the first tower, starting in the fall of 1981, and about $20 a square foot in the second tower when it is completed in 1982. The combined rent initially would be about $8 million a year. Campbell told the commission the leasing plans for the first tower would be void unless the FCC signs a lease with the owner within the next week or two, although he admitted he had not been given a specific deadline.

Several commissioners questined the need for haste, pointing out that such a lease would be conditional in any case, subject to congressional approval next spring. All government leases of more than $500,000 a year must be approved by both the House and Senate public works committees.

Commissioners also questioned Campbell's figures on the savings the commission would realize by moving to Rosslyn. Washburn said he had been informed in the last week that at least one developer has offered to provide the FCC office space in Southwest Washington, near the Mall, for less than the Rossyln rents.

"I just don't believe there's been adequate consideration given to keeping this commission in the federal city," Washburn said. "I'm not suggesting we abandon the option of Rosslyn, but that we investigate other sites."