President Reagan's chief economic adviser has refused to appear during the lame-duck session of Congress before a congressional committee holding hearings on the economy, and thereby has delivered an "insult to the whole Congress," the chairman of the Joint Economic Committee, Rep. Henry S. Reuss (D-Wis.), said yesterday.

Reuss had asked Martin S. Feldstein, chairman of the Council of Economic Advisers, to testify to the JEC last Friday and yesterday. Feldstein was unable to attend either session, a member of his staff said, adding that sufficient notice wasn't given.

Although JEC aides said the committee would be "happy to accommodate Chairman Feldstein's schedule," Feldstein since has refused to offer another time. He wrote to Reuss on Friday, citing pressure of work and his not being confirmed yet by the Senate as reasons "why I will not be able to appear before your committee before the first of next year."

Reuss, a fierce critic of Reagan, retires at the end of this year, and the JEC chairman next year will be Republican Sen. Roger W. Jepsen (R-Iowa). Reuss rejected Feldstein's reasons for refusing to testify, noting that the CEA chairman has made several public and television appearances in recent days. Reuss said that because Feldstein was named to his office during the recent recess, "he is the duly constituted, recess-appointed" CEA chairman and "owes an obligation to the Joint Economic Committee and to any other committee of Congress to appear when called."

Feldstein's staff was "irritated" by Reuss' insistence on scheduling a hearing for yesterday even though the CEA chairman could not attend, sources said yesterday. Feldstein has turned down other requests to testify before Congress until after the Senate votes on his confirmation, a spokesman said. One was a request to appear before a Ways and Means subcommittee on Thursday.

Reuss said that there was no administration policy against officials testifying before confirmation. But Feldstein's aide said "the confirmation bit was an important factor," although he added that the economist could have sought permission to testify had he wished to.

Feldstein was at a Cabinet meeting at the time the hearing was scheduled. A staffer for Reuss said that the congressman had not been told of the reason for Feldstein's unavailability yesterday, and was considering "going ahead with an empty chair" at hearings on Friday to point up the CEA chairman's absence.