The group, founded by Mickey Ibarra, a former Director of Intergovernmental Affairs under President Bill Clinton, specializes in Latino outreach.
Commenting on a New York Times story about Pershing Square's lobbying efforts, Herbalife accused Ackman of running a "cynical, self-serving attempt to manipulate the market by buying his way into an investigation to cover his own reckless $1 billion bet."
Pershing Square said Monday it plans a webcast on an investigation showing "Herbalife's business in China operates much like the company's business in the rest of the world - as a pyramid scheme."
Ackman has accused Herbalife of unfairly targeting minorities. Civil rights group League of United Latin American Citizens, which has asked California's Attorney General to probe Herbalife, echoed the fund manager's accusations. Herbalife said last month that it does not target members of minorities or low income communities.
The battle for the future of Herbalife is heating up this year with each side trying to press its case with Washington lawmakers as well as regulators, who may ultimately control the company's fate.
(Read more: Herbalife bet ourworst ever: Pershing Square)
In the last days, the U.S. Securities and Exchange Commission and the Federal Trade Commission refused to tell U.S. Senator Edward Markey, who asked them to probe the company, what they were doing on Herbalife. But each offered plenty of examples of having shut down illegal businesses before.
SEC chair Mary Jo White, who last year touted the benefits of shareholder activism, said the SEC's Enforcement Division has previously probed whether statements made about a business are "materially false or misleading, including statements regarding the compensation levels."
Ackman has said that 88 percent of Herbalife distributors earn nothing. That stands in stark contrast to some Herbalife distributors' testimonials where they tout lavish lifestyles as an incentive for others to sign up. Herbalife has said distributors results' depend on time, energy and dedication.
Ackman has forecast that Herbalife's share price will plummet to zero amid regulators' scrutiny but so far the fund manager is in the red on the bet, as Herbalife shares have climbed 61 percent in the last year. Since January, the shares have lost ground however, falling 17 percent.
(Read more: Herbalife Q4 earnings, revenue beat; stock rises)