Bill Ackman is taking his campaign against Herbalife to a new level, with sources telling CNBC that the hedge fund manager has filed a complaint with regulators against George Soros, who last week made a big investment in the nutritional supplement maker.
On Wednesday, news surfaced that Soros was taking a large long position in Herbalife. Ackman is now petitioning the Securities and Exchange Commission to address concerns that the legendary investor broke insider-trading rules by alerting other hedge funds about the big investment, sources say.
Since last December, Ackman's Persing Square Capital has maintained an uncovered $1 billion bet against Herbalife, a position that has become increasingly squeezed as the stock has surged by around 60 percent. It has also embroiled Ackman in a bitter public war of words with billionaire investor Carl Icahn, who is long the stock.
—Reporting by CNBC's Scott Wapner, writing by Javier E. David.