Goldman Sachs Group Inc and Chief Executive Lloyd Blankfein were hit with a shareholder lawsuit claiming they hid key details about a risky transaction that resulted in civil fraud charges and a plummet in its stock price.

Monday's lawsuit filed in Manhattan federal court accused Goldman of making materially false and misleading statements about an Abacus collateralized debt obligation tied to subprime mortgages that regulators say it created and marketed though it was designed to lose money.

The complaint also alleged Goldman concealed its receipt of a Wells notice last July from the U.S. Securities and Exchange Commission, indicating potential civil charges over Abacus.

According to the complaint, Goldman's actions caused its shares to trade at inflated levels. The shares fell 12.8 percent on April 16, wiping out more than $12 billion of value, after the SEC filed a civil fraud lawsuit against Goldman.

For anyone to say this type of development is not something a reasonable investor would not want to know simply does not hold water, said Darren Robbins, a partner at Robbins Geller Rudman & Dowd LLP, which filed the complaint.

The lawsuit seeks class-action status and unspecified damages on behalf of potentially thousands of shareholders.

Goldman did not return a request seeking comment. Other executives named as defendants are Chief Operating Officer Gary Cohn and Chief Financial Officer David Viniar.

Goldman Shares closed down $5.37, or 3.4 percent, at $152.03 in afternoon trading on the New York Stock Exchange.

In its lawsuit over the Abacus transaction, the SEC accused Goldman of failing to tell investors that securities underlying Abacus were chosen by billionaire hedge fund investor John Paulson, who was betting that the securities would lose value.

Paulson made about $1 billion on Abacus, roughly the amount other investors are believed to have lost. Goldman called the SEC allegations unfounded and Paulson has not been charged.

BLANKFEIN TO TESTIFY

Blankfein and Fabrice Tourre, a Goldman vice president believed to be the main creator of the Abacus transaction, are scheduled to testify before a Senate panel on Tuesday.

In his prepared comments, Blankfein said: We didn't have a massive short against the housing market and we certainly did not bet against our clients.

Democrats are using the case to try to gain momentum to tighten financial oversight, which President Barack Obama supports.

Robbins said Monday's lawsuit is the first securities fraud case filed against Goldman and seeking class-action status since the SEC sued. Legal experts expect others to follow.

The named plaintiff is Ilene Richman, a Goldman shareholder who Robbins said was extremely troubled by the conduct that went on. She was not immediately reachable for comment.

Last week, Goldman was also hit with two shareholder derivative lawsuits in a New York state court accusing executives and the board of breaching fiduciary duties. Another such lawsuit was filed on Monday in Manhattan federal court.

Shareholders bring derivative lawsuits on behalf of companies to enforce or defend rights that the companies fail to address on their own.

The securities fraud case is Richman v. Goldman Sachs Group Inc et al, U.S. District Court, Southern District of New York, No. 10-03461.

(Reporting by Alexandria Sage and Jonathan Stempel; additional reporting by Grant McCool; editing by Gerald E. McCormick and Andre Grenon)

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