Shares of Blackstone Group LP, the private equity firm that went public late last month, fell as much as 7 percent on Friday, amid a debt market freeze that has shut off funding for leveraged buyouts. Blackstone's stock has fallen 21 percent since its June 21 debut, making it one of the year's worst performers for U.S. IPOs.

Its shares were down another 7 percent on Thursday, before staging a late-day rally, ending slightly higher. The firm's stock fell 4.8 percent on Friday afternoon to $24.44.

Blackstone raised more than $4 billion through its IPO, most of which went to paying out top partners.

Shortly after Blackstone priced its IPO, debt investors began pushing back against the leveraged buyout financing. Banks that loaned private equity firms such as Blackstone billions of dollars for buyouts suddenly had trouble get debt investors to purchase the loans.

Now, more than $200 billion worth of debt is being held by banks and waiting to be sold down to investors sometime after the U.S. Labor Day holiday in early September.

Blackstone's slide on Friday followed a broad market decline, with all three major U.S. indexes down more than 1 percent on concerns about the broadening deterioration in credit markets.

Investment