A divided Federal Communications Commission, citing growing pains and economy considerations, yesterday voted to move its headquarters and 1,700 employes out of Washington and into two Rosslyn high-rise buildings.

The hotly-debated proposal to lease 22 floors of Rosslyn's 30-story Twin Towers to solve the agency's space problems had been urged by the FCC staff and Commission Chairman Charles Ferris for almost a year. Until yesterday the move, dubbed "Project Exodus," had never officially been voted on by the commission.

The agency's annual rent in Rosslyn would be $6.8 million -- a relative bargain compared to the District of Columbia's costlier rates, according to proponents of the plan.

If Congress approves the move -- and at least one congressional committee is expected to hold hearings on it -- the FCC headquarters at 1919 M St. NW would be vacated in early 1983.

In a strongly-worded statement, Commissioner Abbott Washburn, who cast the lone dissenting vote, attacked yesterday's action as "premature and unfortunate . . . [it] opens the commission to charges of irresponsibility." He also criticized the contract given a private firm to negotiate the government lease, a lease he said "was negotiated without knowledge of the five present commission members" (excluding Ferris).

Washburn said the decision, voted in a closed session, was made "largely on the basis of price despite the absence of firm figures for comparsion." At least two downtown Washington office buildings apparently are available at comparable rental rates, Washburn said.

Washburn and the National Treasury Employes Union, which represents most FCC employes, have urged that the FCC remain in downtown Washington for the convenience of agency employes and those who deal with the commission.

The agency's 1934 charter requires that it be headquartered in the District. Last year, however, the FCC successfully lobbied Congress to grant independent leasing authority to the agency and also to "redefine" the District to include any area within two miles of city boundaries.

Following the 4-1 commission vote, acting Chairman Robert E. Lee told reporters, "There is no feasible alternative to Rosslyn. I hope this spells the end of this controversy, although I doubt it will."

Ferris, who retains the title of chairman until President Reagan designates his successor, abstained from the vote. Reagan has yet to appoint the commission's seventh member, to replace Tyrone Brown, who resigned last month.

Lee said "the space situation is critical" for the agency, whose employes now work in five buildings in a fast-growing and increasingly expensive area around Connecticut Avenue. He estimated that leasing space in downtown Washington would cost a minimum of $250,000 more per year than in Rosslyn.

Washburn yesterday repeated criticisms that the agency would be moving into buildings originally opposed by the federal government on grounds they mar the historic skyline of the nation's capital.

The Interior Department unsuccessfully attempted to block construction of the towers in a 1979 court suit.