Michael Avenatti said Monday evening that his client, Julie Swetnick, did not witness first-hand Supreme Court nominee Brett Kavanaugh allegedly spiking the punch at high school parties in the early 1980s. But he knows a woman who claims to have seen the act, and while she is willing to speak to the FBI, she won't go public.

Avenatti, who is also the lawyer to porn star Stormy Daniels, made an appearance on CNN and was pressed to answer to doubts about Swetnick's credibility. During this conversation, host Chris Cuomo asked him to answer to an NBC News interview Swetnick did, in which she appeared to contradict a claim she made against Kavanaugh in a sworn declaration last week.

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"Well, I saw him giving red Solo cups to quite a few girls during that time frame and there was green punch at those parties," she said. "And I would not take one of those glasses from Mark Kavanaugh -- Brett Kavanaugh, excuse me. I saw him around the punch — I won't say bowls, or the punch containers. I don't know what he did, but I saw him by them, yes."

In her sworn declaration, Swetnick implicated both Kavanaugh and his high school friend Mark Judge: "I became aware of efforts by Mark Judge, Brett Kavanaugh and others to spike the punch at house parties that I attended."

After airing both, Cuomo said, "I argue that they're different." Avenatti then got a crack at explaining.

"Well, what her testimony stated and the declaration — I understand you — are used different. One of her friends informed her of what she just put in the declaration or what was attested to in the declaration," Avenatti said before going on to mention another potential witness.

"And last night at 10:40 p.m., I had a telephone conversation with a woman who will go unnamed, who lives in Florida, who told me directly that Mark Judge and Brett Kavanaugh would spike the punch with grain alcohol and Quaaludes," he continued.

Avenatti emphasized that this woman knows what happened "because she saw it. And it's about the fifth conversation I've had with her in the last two weeks."

When asked if this woman would come forward to the FBI, Avenatti said "100 percent," adding that she "doesn't want to be outed publicly."

Avenatti has called for the FBI to interview his client, who also says she was "gang raped at a party where Kavanaugh was present," along with two other women accusing Kavanaugh of sexual misconduct.

After this supplementary probe is completed, likely this week, the Senate is poised to vote on Kavanaugh's nomination.