Goldman Sachs, the embattled investment bank, will face an array of legal claims focusing on its conduct during the financial crisis, one of Wall Street's most feared lawyers warned last night.

The prediction of an escalation in cases is being made by Jake Zamansky, the US attorney nicknamed "Jaws" who spearheaded the successful pursuit of the investment banks after the dotcom crash. It follows a move by Lloyd Blankfein, the chief executive of Goldman Sachs, to hire Reid Weingarten, one of America's top criminal defence lawyers, to help him address claims that the bank misled clients in the run-up to the financial crisis and, afterwards, Congress.

"I consider this to be a very significant event. For Lloyd Blankfein to be hiring a top criminal lawyer indicates that there may be allegations of wrongdoing forthcoming from the Department of Justice [DoJ]," Zamansky said. "Investors are asking why there have been no criminal cases against Goldman Sachs or any investment bank arising from the financial crisis. This may be a sign of more cases to come. It may be the beginning of a series of cases against Wall Street firms".

Back in 2001, as the internet bubble was bursting, Zamansky filed the very first lawsuit against Merrill Lynch's Henry Blodget, then a top-rated technology analyst caught pushing shares to investors which internal emails showed he actually rated as "dogs". The case proved to be a catalyst for a legal assault on Wall Street which resulted in the banks signing some huge cheques.

Zamansky is representing a group of un-named investors suing Goldman, although the case is unrelated to the bank's battles with the DoJ.

However, other moves to pursue the investment bank and its directors are under way, with court documents showing that Blankfein and his fellow directors have been named in a derivative court action filed in New York by an individual investor called Michael Brautigam. Counsel for the defendants, who also include Goldman non-executive and steel tycoon Lakshmi Mittal, have been asked by District Judge William H Pauley III to appear in court next month for a pre-trial conference. As this is a civil case, Weingarten will not be representing Blankfein. The derivative action formed part of a 12-page report detailing the current legal cases the bank is facing, which Goldman outlined in a regulatory filing this month.

The document goes on to admit: "The firm expects to be the subject of additional putative shareholder derivative actions, purported class actions, rescission and 'put back' claims and other litigation, additional investor and shareholder demands, and additional regulatory and other investigations and actions with respect to mortgage-related offerings, loan sales, CDOs [collateralized debt obligations] and servicing and foreclosure activities".

Shares in Goldman fell in late trading on Monday after Weingarten's appointment emerged – shedding 4.7% to $104.25, their lowest level since April 2009.They had dropped again on Tuesday.

Blankfein turned to the high profile lawyer after the DoJ began investigating the way Goldman sold subprime mortgages – the toxic investments that triggered the credit crunch. The banker has also been accused of misleading a Senate committee – a claim that is emphatically denied by Goldman. Blankfein has not been charged with any offence. Goldman itself was charged in April 2010 with defrauding investors of more than $1bn (£606m), and later paid a $550m fine. In June, the bank was served with a subpoena by the Manhattan prosecutor.

"As is common in such situations, Mr Blankfein and other individuals who were expected to be interviewed in connection with the justice department's inquiry into certain matters raised in the [Senate] report hired counsel at the outset," said a Goldman spokesman.

Weingarten specialises in white-collar criminal defence, and has represented former WorldCom chief executive Bernard Ebbers and former Enron accounting officer Richard Causey. Both men are incarcerated after being convicted of fraud charges.

The website of Steptoe and Johnson, the firm where Weingarten is a partner, states that the lawyer "is part of the firm's white-collar criminal defence group". It continues: "Weingarten represents clients in complex criminal matters in both state and federal courts at the pre-trial, trial, and post-trial stages, including cases involving public corruption, the Racketeer Influenced and Corrupt Organizations Act, bank fraud, bribery, government procurement fraud, antitrust, healthcare fraud, and tax and securities fraud."