David Einhorn’s Greenlight Capital cranked up the pressure on General Motors on Thursday by launching a website that encourages shareholders to vote for the hedge fund’s proposal.

GM rejected Greenlight’s plan in March to appoint three directors to GM’s board and divide the common stock into two classes. Now the hedge fund’s newly launched website, UnlockGMValue.com, calls for investors to “VOTE GREEN CARD TODAY.”

GM’s annual shareholder meeting is scheduled for June 6. GM did not immediately return a CNBC request for comment.

Shares of the automaker fell 1 percent in morning trade and are down 4.9 percent this year.

Website landing page

The proposal “would unlock tens of billions of dollars of shareholder value and was specifically designed not to change GM’s business strategy, capital allocation priorities or financial policy,” according to the website.

Greenlight owns 3.6 percent of GM common stock, making it the fifth largest public shareholder of the auto manufacturer.

The hedge fund returned just 1 percent in the first quarter, trailing the S&P 500’s 6 percent gain, according to the hedge fund’s letter sent to shareholders last week.