Goldman Sachs on Wednesday rebuffed claims made by a former company executive that the investment bank had morphed into a “toxic and destructive” environment where corporate greed trumped client interests.

In an essay published in the New York Times, Greg Smith, a Goldman executive director, bashed the Wall Street firm, including chief executive Lloyd Blankfein and president Gary D. Cohn, for allowing the company to lose its “moral fiber.”

“It makes me ill how callously people talk about ripping their clients off,” Smith wrote.

Blankfein disputed his former employee’s description of the firm’s culture.

In a letter to his staff, the chief executive wrote, “We were disappointed to read the assertions made by this individual that do not reflect our values, our culture and how the vast majority of people at Goldman Sachs think about the firm and the work it does on behalf of our clients.”

Before the recession, Goldman enjoyed a near-pristine image, and its top executives such as Henry M. Paulson, Robert Rubin and Jon S. Corzine moved easily into prominent government posts after leaving the firm. But the financial crisis blemished that reputation, and this episode marks another challenge to restoring it.

The dust-up comes as federal regulators gear up to forge the final terms of the so-called Volcker Rule, a policy that could ultimately cost Goldman Sachs and other investment banks billions of dollars.

The criticism could also raise questions about what kind of leader Blankfein has been since taking the helm of the Wall Street firm in 2006.

“From a public relations standpoint, at a crucial time for Goldman Sachs, this is very harmful for them,” said Andrew Stoltmann, a securities attorney who has litigated against the investment bank.

Smith, who had worked in London overseeing an equity derivatives business, also wrote that some leaders at Goldman referred to their clients as “muppets” and that workers were rewarded for a practice dubbed “hunting elephants,” in which Smith says the goal was to get clients to trade any security that would net Goldman the largest profit.

Goldman’s shares sank 3.35 percent in regular trading on a day of mixed stock performances for the nation’s biggest banks. After the markets closed Tuesday, the Federal Reserve announced that 15 of 19 banks, including Goldman Sachs, had passed its latest round of stress tests.

Not all analysts agreed with the portrait Smith painted of Goldman.

“The characterization that clients are ‘muppets’ and they’re just sucking them dry and this and that, maybe that was [Smith’s] experience, but it certainly wasn’t mine,” said Phil Orlando, chief equity market strategist at Federated Investors in New York and a longtime client of Goldman Sachs.

Goldman Sachs is not the only Wall Street institution that has been the target of vitriol in the wake of the 2008 financial crisis.

“This issue has been kind of swirling around the news and it’s an issue that has been facing the financial industry for years,” said Jack Ablin, chief investment officer at Harris Private Bank in Chicago. “This is a conflict of short-term profits against longer-term goals.”

In recent years, Goldman Sachs has had to gird itself against other harsh accusations of corporate greed. In a 2010 Rolling Stone article, journalist Matt Taibbi famously described the investment bank as “a great vampire squid wrapped around the face of humanity, relentlessly jamming its blood funnel into anything that smells like money.”

Sen. Carl Levin (D-Mich.) described Goldman Sachs as a “financial snake pit” last year after he led a panel that examined the origins of the 2008 crisis.

Chief executive Lloyd Blankfein drew criticism in November 2009 after he told the British newspaper the Times that he was “doing God’s work” at Goldman.