Where does investigative reporting end and exploitation begin? ''The Mike Wallace Profiles: Jean Seberg'' (CBS, Tuesday, 10:30-11 p.m., check local listings) is the first in an irregularly scheduled new series of ''biographical inquiries'' to be conducted by that dependably tough interviewer, Mike Wallace.
But the late Miss Seberg's story has been chronicled in every scandal publication for some time, and this Mike Wallace ''Profile'' is out-and-out exploitation of very distasteful episodes in the life of this unhappy woman, allegedly hounded to suicide by what the show charges are FBI smears. Mr. Wallace retraces all of the facts and fictions, then evokes tears from her parents as they discuss the seemingly great injustices done to their child.
Since most of the facts are already common knowledge, the program is an embarrassing redundancy, of interest only to those who may revel in its rehash of unhappiness and dissolution. It is unworthy of a man whose hard-hitting investigations many have come to respect on ''60 Minutes.''