Trump attorney Rudy Giuliani unloaded on former Trump lawyer Michael Cohen on "Fox News Sunday," saying Cohen is a "scoundrel" and "total liar."

The comments came as porn star Stormy Daniels' attorney also unleashed a broadside at Giuliani, calling him "buttercup" and telling him to "buckle up" as the ongoing drama with Cohen and his secretly recorded audiotapes unfolds.

"I should say I feel sorry for him, but no one will believe me," Giuliani said, referring to Cohen. "He's destroyed himself as a witness. I have prosecuted 5,000 cases. I would never prosecute a case on this guy’s testimony."

Giuliani added that he thinks Cohen is "capable, I think, unfortunately, of doctoring tapes" -- echoing his claim from last week that two experts and retired FBI agents have analyzed the secretly recorded Trump-Cohen tape and believe it was “played” with.

The statements marked the continuation of a sharp about-face by Trump's team on Cohen. In May, Giuliani had told ABC's "This Week" that Cohen is an "honest, honorable lawyer." Guiliani explained the change of heart by telling host Chris Wallace on Sunday he didn't realize Cohen was a "pathological liar" until he released secretly recorded conversations with this then-client, President Trump.

Giuliani called that a "disbarrable offense," and rejected arguments that Trump's team had waived attorney-client privilege by discussing the tape in public.

"The court order allows us to respond without waiving any privilege," Giuliani said. "After all, it’s not my privilege – it’s the president’s privilege – if we have to defend him; that’s exactly what we were doing."

Responding to the interview, Cohen attorney Lanny Davis sent a statement to Fox News disputing Giuliani's claim.

“Mr. Giuliani seems to be confused," Davis said, repeating a previous statement. He expressly waived attorney client privilege last week and repeatedly and inaccurately — as proven by the tape —talked and talked about the recording, forfeiting all confidentiality claims.”

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Separately, Giuliani took issue with the idea that Supreme Court nominee Judge Brett Kavanaugh, who has previously written that investigations can unduly distract presidents while in office, would help Trump legally if confirmed.

"I believe that the Constitution is clear that the president cannot be subpoenaed or, if he is subpoenaed, he has a right to challenge it on the grounds, if they haven’t exhausted all other possibilities," he said. "I wouldn’t count on Kavanaugh’s vote on this. This is a question of first impression. And the Trump situation is very different than the Nixon situation. So I don’t think we get an edge one way or the other.

"There’s a case, the [Mike] Espy case, closest one you can find, he was a Cabinet officer and they said he can only be subpoenaed, in essence taken away from his duties, if there was no other way to get the information," Giuliani said. "So the president would at least have that privilege. Whether he has a complete privilege and therefore can’t be investigated at all -- I really would have to do more research."

Giuliani also conceded there would be something wrong on an "ethical, moral basis" if President Trump was misleading the public by claiming he did not know in advance of a disputed June 2016 meeting at Trump Tower with a Russian attorney.

Trump Jr., his brother-in-law Jared Kushner, and then-campaign chairman Paul Manafort were known to have attended the meeting with Kremlin-linked attorney Natalia Veselnitskaya. Email records released by Trump Jr. showed that the meeting was billed as an opportunity to reveal dirt on Hillary Clinton as “part of Russia and its government’s support for Mr. Trump.”

Meanwhile, porn star Stormy Daniels' attorney, Michael Avenatti, took aim at Giuliani on Twitter Sunday, calling him "desperate."

".@RudyGiuliani -- Are you denying that there were other hush payments made to as yet unnamed women in connection with the 2016 campaign?" he wrote. "Asking for some friends... You better buckle up buttercup because Mr. Trump’s stupidity and disloyalty is about to catch up to him (and you)."

Avenatti also disputed the idea that Cohen's credibility was damaged.

"Rudy -- you look desperate, bc you are. What are you & Mr. Trump so afraid of if he did nothing wrong as you claim? Releasing the info in no way damages Cohen’s credibility or usefulness as a witness," he wrote. "But it will severely damage Trump. And we are just getting started. #FightClub."