Labor Secretary Raymond J. Donovan, in an move that could signal the start of a major reorganization of the Labor Department, yesterday downgraded the Employment Standards Administration by naming a deputy undersecretary to head the agency.

ESA, which is responsible for the administration of workers' compensation, wage and hour, and affirmative action laws affecting federal contractors, had been staffed at the higher, assistant secretary level in recent administrations.

The new appointee is Robert Burns Collyer, 48, a lobbyist for the Washington-based Unemployment Benefits Advisers, Inc., an organization representing management interests in unemployment compensation and related matters.

Though ESA's agency head status has been downgraded, Earl G. Cox, Donovan's spokesman, insisted yesterday that the move "does not, in any way, suggest a deemphasis or dismantling of the ESA's final programs.

"In the case of some Labor Department appointments, we are maintaining flexibility in case there is a need for a reorganization," Cox said. "As we do so, we are reviewing the overall department structure and keeping management options fluid," he said.

Cox added: "Appointing a deputy undersecretary rather than an assistant secretary to head the Employment Standards Administration suggest there could be some restructuring of this organization in the future."

Still, Donovan's actions yesterday seem consistent with Reagan transition team suggestions last January that ESA and several other agencies be downgraded indepartmental standing.

Reagan transition team sources said then that the then-incoming administration was considering farming out ESA responsiblities, such as the agency's workers compensation programs, to the assistant secretary of the Labor Management Services Administation. Sources said civil rights compliance activities, now vested in ESA's Office of Federal Contract Compliance Programs, would become the direct responsibility of the labor secretary under a new arrangement.

However, other sources inside the Labor Department discounted the notion that Donovan would take direct control of OFCCP, on the ground the agency is too controversial and could prove politically embarrassing in a hot dispute over women/minority hiring. "It would be like placing a ticking bomb underneath his bed," one source said.

Donovan himself has not publicly discussed his plans for OFCCP. For example, in a recent interview, he would only say: "I can honestly tell you that I have not addressed myself to that problem."

There have also been suggestions the Donovan had planned to downgrade or dismantle the office of the Assistant Secretary for Policy Evaluation and Review (ASPER), the Labor Department's research arm, used especially in economic planning matters.

However, Donovan dismissed those suggestions in an interview. "As a matter of fact, it is my personal opinion that ASPER has been under-appreciated and under-utilized," he said during a meeting with reporters last February.