Already grappling with regulatory reviews of its troubled initial public offering, Facebook Inc. and the Wall Street banks that shepherded the deal are now under fire from lawmakers and lawyers. Two congressional committees said on Wednesday that they would conduct preliminary inquiries into the IPO. And attorneys filed two separate lawsuits alleging that average investors were misled in the days before Facebook shares began trading last Friday. \"Shareholders suffered billions of dollars in losses,\" said Darren Robbins, a partner in the San Diego law firm of Robbins Geller Rudman & Dow, which filed one of the suits.\"To have what was perceived as a watershed IPO result in this kind of harm is deeply troubling.\" Facebook has vowed to defend itself vigorously against shareholder suits. And the Menlo Park, California, company reportedly was considering moving its stock listing to the New York Stock Exchange from the Nasdaq Stock Market, whose technical glitches executing trades on Friday added to the IPO\'s woes. Facebook shares rose $1 on Wednesday to close at $32, a 3.2 per cent gain. But the shares were still trading well below the IPO price of $38. A revised revenue forecast issued by Facebook only days before its initial public offering has become a flash point for investors, regulators and lawyers. Robbins Geller, which recovered $7.2 billion for Enron shareholders in 2008 in the largest-ever class-action settlement, sued on behalf of three Facebook shareholders. It was the most high-profile of at least three suits seeking class-action status filed this week. The suits alleged that Facebook Chief Executive Mark Zuckerberg and the banks underwriting the IPO concealed crucial information shortly before the social networking company went public. The Robbins Geller lawsuit, filed in the US District Court in Manhattan, accused the defendants of failing to disclose fully before last Friday\'s IPO a revised forecast showing that revenue would not be growing as anticipated because users were moving to mobile devices that can\'t display as many ads. Meanwhile, regulators are examining whether investment banker Morgan Stanley, the lead underwriter, selectively informed clients of an analyst\'s negative report about the company before the stock started trading. Regulatory authority The Securities and Exchange Commission and the Financial Industry Regulatory Authority, the self-policing body for the securities industry, said their agencies are looking into the events surrounding the IPO. Rick Ketchum, the head of Finra, said on Tuesday that the question is \"a matter of regulatory concern.\" Neither the SEC nor Finra would provide additional details. \"Until we unwind the facts and circumstances surrounding this situation, it is inappropriate to speculate about what potential violations may have occurred,\" a Finra spokesperson said on Wednesday. The Robbins Geller suit focuses on what it alleged was the failure of the companies to disclose to all investors that Facebook was \"experiencing a severe and pronounced reduction in revenue growth due to an increase of users of its Facebook app or website through mobile devices rather than a traditional PC.\" The suit alleges that Face-book had told the lead underwriters of the IPO to reduce their 2012 estimates for the company and that information was \"selectively disclosed\" to preferred investors and left out of the prospectus and registration statement. \"The notion that the lead underwriters would contemporaneous with a road show and a filing of the registration statement receive information and thereafter materially reduce revenue projections for the very period the IPO occurred is nothing less than shocking,\" Robbins said.