Einhorn, who runs hedge fund Greenlight Capital, also said U.S. lawmakers seeking answers to how day traders were able to wrest control of GameStop's share price from established hedge funds should probe regulators instead of investors.

Amateur investors organized on social media sites such as Reddit staged a stubborn buying spree three months ago, winning out over Wall Street hedge funds that had shorted GameStop's shares or bet that the price would fall.

The wild price swings caused heavy losses for hedge fund Melvin Capital, among others. U.S. lawmakers reacted by organizing a U.S. House of Representatives hearing in February where they quizzed hedge funds, a day trader and the chief of the online trading app Robinhood.

Einhorn on Thursday blamed Palihapitiya and Tesla Inc's CEO, Musk, for throwing what he called "jet fuel on the GME squeeze." His comments appeared in a quarterly letter to Greenlight Capital investors which was seen by Reuters.

Representatives for Palihapitiya and Musk did not immediately respond to requests for comment.

Einhorn said it is appropriate for investors to discuss stocks.

"Investors discussing why they think GameStop (or any other stock) should go up or down ought to be encouraged," he wrote. "There is no reason to drag anyone before Congress for making a stock pick."

Einhorn said Palihapitiya, who appeared on TV in late January and dismissed criticism of day traders, might have been trying to harm Robinhood because it competes with fintech startup SoFi, which was backed by Palihapitiya.

And Musk, whose Tesla shares Einhorn has long bet against, waded in to the drama by tweeting "Gamestonk!!" and adding a link to the Reddit forum where day traders were discussing GameStop.

"If regulators wanted Elon Musk to stop manipulating stocks, they should have done so with more than a light slap on the wrist when they accused him of manipulating Tesla's shares in 2018," Einhorn wrote.

Einhorn said if lawmakers wanted to understand "why GameStop did what it did ... it would be better to call to account the absentee regulators and their philosophical backers."

He told investors that his Greenlight Capital Funds were essentially flat in the first quarter, inching down 0.1%, while the S&P500 index gained 6.2%

(Reporting by Svea Herbst-Bayliss in Boston; Editing by Matthew Lewis)

By Svea Herbst-Bayliss