"I don't have any involvement," Dunlap told New York's Daily News.
Dunlap, a managing partner at Dunlap, Grubb & Weaver, had been trying to sell the tape to British and U.S. news organizations for $250,000-$2 million, the Daily News reported.
Dunlap, on behalf of the unidentified tape's owner, previously had shown reporters 90 seconds of a 43-minute tape that Dunlap claimed was legally obtained by a "friend" of Ashley Biden's who allegedly filmed her taking drugs this year at a private party in Wilmington, Del.
Dunlap reportedly broke ties with his client Sunday due to the intense coverage the story has generated, the newspaper said.
There has been no comment from the White House, the vice president's office or Ashley Biden, 27, a social worker with the Delaware Department of Children, Youth and Families, the Daily News said.