President Carter is expected to name Robert Pitofsky to be a member of the Federal Trade Commission, source said yesterday.

Pitofsky, a professor of law at Georgetown University who is associated with the Washington law firm of Arnold and Porter, will be nominated to fill a vacancy on the commission created at the end of December when Calvin J. Collier resigned.

Pitofsky, 48, is no stranger to the commission. He served as director of the FTC's Bureau of Consumer Protection in the early 1970s under former chairman Miles W. Kirkpatrick. American Bar Association panel, which Kirkpatrick headed, that had concluded the FTC should be abolished if it couldn't be reformed.

It was under Pitofsky's direction that the bureau of consumer protection began to seek innovative remedies to correct false advertising and othe runfair practices. Pitofsky also put together a transition book on the agency for the incoming Carter administration.

Before coming to Washington, Pitofsky was a New York University law professor.

The White House had winnowed down a large field of candidates it was considering to two before Pitofsky was picked, sources said. The other candidate was Willard Mueller, an economist at the University of Wisconsin wjjo had served as director of the FTC's Bureau of Economics in the 1960s