Ackman: Icahn Wanted to Be My Friend, I Said No

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Bill Ackman CEO of Pershing Square Capital Management LP.

Billionaire activist investors and longtime rivals Carl Icahn and Bill Ackman are at it again.

This time, the two are tangling over Ackman's short position in Herbalife, a debate that extended itself into barbs over a 10-year-old legal dispute.

In a televised appearance Thursday, Icahn ripped Ackman for publicly revealing a large bet against Herbalife late last year. Icahn reportedly has taken a long position in the company.

(Read More: Billionaire Carl Icahn Takes Herbalife Stake: Reports)

In a CNBC interview last month, Ackman labeled the company, which sells weight-loss and nutrition products, a pyramid scheme. He said he had borrowed more than 20 million shares to sell, later hoping to buy them back at a lower price and pocket the difference, a process known as short-selling.

The public nature of the move was "disengenous," Icahn said in a Bloomberg television interview Thursday in which he said he neither liked nor respected Ackman.

In a rejoinder of his own, Ackman released a statement recounting how their dispute went back to a 2003 court case in which Icahn lost.

That suit involved a deal between Ackman's former firm, Gotham Partners, in which Icahn brought a 15 percent stake in Hallwood Realty Partners and issued "schmuck insurance" that guaranteed Gotham investors 50 percent of Icahn's profit if he sold his stake within three years. That payout would have come after Icahn received a 10 percent annual return.

Icahn did sell within that time period but allegedly refused to pay off and lost multiple court decisions after Ackman's side sued.

When the case was finally resolved, Ackman said Icahn called "and said that he wanted to be my friend."

(Read More: From High Energy Clubs to Dashed Dreams: Herbalife Tales)

"I told him that I had no interest in being his friend," Ackman said. "Carl Icahn is a great investor, but, in my experience, he does not keep his word."

The Icahn matter is the second public feud in which Ackman has been involved recently.

He also has gone head-to-head with hedge fund manager Dan Loeb, who has taken a long position in Herbalife. Other investors also have challenged Ackman's position.