Late last week, ABC News came under fire for allowing discredited conservative Andrew Breitbart to participate in their election night coverage. (ABC later announced he would only appear online.)

Now Breitbart's websites are accusing an Alaska CBS affiliate of gross journalistic misconduct by alleging the station's assignment editor and reporters were “conspiring to set up some type of smear of Joe Miller,” the Republican nominee for the U.S. Senate seat in Alaska. The allegations stem from a partial voicemail recording posted on the site.

KTVA, the station in question, is denying the charges, saying, “the allegations are untrue.” General Manager Jerry Bever said, “The complete conversation was about what others might be able to do to cause disruption within the Miller campaign, not what KTVA could do.”

Breitbart, as you'll recall, has become infamous for promoting deceptively edited videos mercilessly smearing Shirley Sherrod as a racist and falsely accusing ACORN of aiding in child prostitution nationwide. And even when not releasing deceptively edited tapes, Breitbart has a long history of flat-out lying.

He also served as a mentor to and promoter of James O'Keefe, the criminal who allegedly planned to sexually harass CNN reporter after trapping her on a boat filled with sex toys.

Before hosting Breitbart on Tuesday, ABC News must investigate the veracity of his claims and demand his site publish the entire voicemail message. Moreover, ABC is obligated to determine whether Breitbart's site is lying about the topic and context of the conversation.

ABC News put its credibility on the line when it offered a noted liar like Breitbart a platform to spread his misinformation. Now it's their responsibility to verify his accusations and hold him accountable for what he says.