И снова HLF

Activist investor Bill Ackman — now almost $300 million in the hole on his $1 billion short bet against Herbalife — is digging in.

Ackman told investors in his second quarter letter, which The Post has obtained, that he has made “material progress” in attracting federal, state and international regulatory interest in the company he believes is a pyramid scheme.

“We are not at liberty to disclose the nature of those developments, but we believe that the probability of timely aggressive regulatory intervention has increased materially.”

Ackman noted that the Securities and Exchange Commission, which the company has said has opened an inquiry into Herbalife, has prosecuted pyramid schemes, including one of the seminal pyramid cases.

The letter, written after an ugly public battle with another big investment, JCPenney, led Ackman to resign from its board last week, started with the admission, “We are going to make mistakes.”

But Ackman said he hasn’t made many in his career of activist investing, and he doesn’t think Herbalife is one of them,

Ackman is now boring in on product-quality issues of the nutritional supplements company and said he has been contacted by two “whistle-blowers” on product-safety concerns.

The 47-year-old New York hedge fund titan revealed that Herbalife products have had 14 to 21 times as many health-related complaints that required hospitalization or emergency room treatment as competitors, according, he said, to documents from the Food and Drug Administration obtained earlier this year through Freedom of Information Act requests, which he attached to the letter.

Three of the so-called “adverse events” were “life-threatening” and two were described as “abortion spontaneous,” he wrote in Pershing Square’s 23-page quarterly letter.

More than eight pages were devoted to Herbalife.

The FDA documents he received compare Herbalife’s best-selling Formula 1 and Herbalife Personalized Protein Powder to those made by Ensure and SlimFast, two other dietary-supplement/weight-loss products, he said in the letter.

“Pyramid schemes like Herbalife [are] particularly vulnerable to product-quality concerns,” Ackman told his investors, noting that Herbalife must recruit about 2 million new distributors a year to fill out its¬ 3.2 million-strong roster — because of massive turnover.

Each new distributor recruit must purchase several thousands of dollars of product in order to receive royalty checks, he said in the letter.

Herbalife has denied it is a pyramid scheme and stands behind its products.

The Herbalife products subject to the FOIA request were manufactured in the company’s Lake Forest. Calif., facility, which it purchased in 2009. A former senior Herbalife employee at the plant has come forward as a whistle-blower on the product issue, discussing problems with lead contamination, among others, Ackman said in the letter.

The whistle-blower has been subpoenaed by New York Attorney General Eric Schneiderman, according to publicized reports. Ackman said his firm recently had been contacted by a second product-related whistle-blower.

Herbalife last week responded to the whistle-blower’s publicized complaints, saying no tainted product was ever shipped to consumers.

In the letter, Ackman also laid out 26 activist positions Pershing Square has taken, and the earnings made when it exited. Only three long position of the 26 — Borders, Target and JCPenney — were losers, he said.

Not counting Herbalife, which is not over, all but one short position — Fannie Mae — was a winner.

“We are fortunate to have made only a few mistakes in our activist commitments over the last nearly 10 years,” he said.