Mitt Romney’s Bain problem just got a lot worse.

According to a new report by Mother Jones’ David Corn, Bain Capital made a $75 million investment in Stericycle — a medical waste disposal firm that has been attacked by right wing groups for disposing of aborted fetuses — while Romney was still actively involved in the company in 1999. This news is sure to upset social conservatives, and it also directly contradicts Romney’s account of when he left Bain.

Romney’s connection to Stericycle was first reported in January by The Huffington Post, but the story never gained traction because Bain Capital claimed that Romney left the firm to run the Winter Olympics in February of 1999 — meaning that he had nothing to do with the deal. According to SEC documents unearthed by Corn, however, Romney was still actively involved in the firm’s leadership through the end of that year:

The SEC filing lists assorted Bain-related entities that were part of the deal, including Bain Capital (BCI), Bain Capital Partners VI (BCP VI), Sankaty High Yield Asset Investors (a Bermuda-based Bain affiliate), and Brookside Capital Investors (a Bain offshoot). And it notes that Romney was the “sole shareholder, Chairman, Chief Executive Officer and President of BCI, BCP VI Inc., Brookside Inc. and Sankaty Ltd.”

The document also states that Romney “may be deemed to share voting and dispositive power with respect to” 2,116,588 shares of common stock in Stericycle “in his capacity as sole shareholder” of the Bain entities that invested in the company. That was about 11 percent of the outstanding shares of common stock. (The whole $75 million investment won Bain, Romney, and their partners 22.64 percent of the firm’s stock—the largest bloc among the firm’s owners.) The original copy of the filing was signed by Romney.

Another SEC document filed November 30, 1999, by Stericycle also names Romney as an individual who holds “voting and dispositive power” with respect to the stock owned by Bain. If Romney had fully retired from the private equity firm he founded, why would he be the only Bain executive named as the person in control of this large amount of Stericycle stock?

As Corn points out, the SEC documents have implications that reach farther than Stericycle. The Romney campaign repeated its assertion that Romney left Bain in February 1999 when rebutting a recent Washington Post story reporting that Bain acquired companies that outsourced jobs. According to these SEC filings, that is not true.

The issue here is not that Romney was investing with a company that disposed of aborted fetuses; after all, abortion is legal, something must be done with the medical waste produced by them, and according to Corn the investment was quite profitable for Bain and its investors.

The issue is that Romney has once again been caught in a lie about his past, and once again given voters a reason for suspicion over his record at Bain — which he has made the central pillar of his campaign.

Romney is already having a difficult time talking about his tenure as governor of Massachusetts, given that he is now running against the health care reform that became the signature achievement of his one term. If voters reject his version of the Bain Capital story as well, then the entire rationale for his candidacy will be undermined.