Buchanan denied the allegations by Sam Kazran, as well as Kazran's claim that Buchanan pressured him into signing a false affidavit regarding illegal campaign contributions.
The independent Office of Congressional Ethics asked the ethics panel to investigate Buchanan in January 2012 after finding there was "substantial reason to believe" that Buchanan attempted to influence Kazran's testimony in a proceeding before the Federal Election Commission.
The ethics panel said in its report that there was insufficient evidence "to show precisely what role ... if any" Buchanan had in drafting an affidavit used in the FEC proceeding.
The committee said in its 26-page report that Buchanan "could not explain the unusual pattern of reimbursed contributions from multiple corporate entities with which he was affiliated." The committee said it does not believe that such violations are "bound to occur" in any campaign, as Buchanan asserted in testimony before the ethics panel.
The committee's report was issued by Reps. Charles Dent, R-Pa., and Linda Sanchez, D-Calif. Dent chairs the ethics panel while Sanchez is its senior Democrat.