The man, identified only as Johan in a report published by the Swedish newspaper Aftonbladet, said a high-ranking police official approached him and asked him if he would shoot Palme a few months before the Social Democrat was actually gunned down in central Stockholm.
The report was written by Gunnar Wall, a journalist who has written two books about the Palme assassination.
But skeptics said such conspiracy theories are a dime a dozen, TheLocal.se reported Monday. Criminologist Leif G.W. Persson said anonymous theories mean little.
"It's far too abstract and vague," Persson said. "He doesn't want to say who the policeman is. The next question is clearly: 'What is the name of the person who asked you to do this?'"
The police officer was not identified in the report.
More than 130 people, from a plumber to a restaurant owner, have confessed to killing Palme. The unsolved case remains an active investigation in Sweden.