An executive director at investment giant Goldman Sachs resigned via a scathing op-ed in the New York Times on Wednesday, decrying a work environment he described as “toxic and destructive” where employees systematically try to come up with ways to fleece their clients.

Greg Smith’s firebomb is certain to renew debate in the United States about how much Wall Street has truly changed four years after shady lending practices by investment firms resulted in a widespread financial meltdown that brought the country to the brink of a depression.

“I attend derivatives sales meetings where not one single minute is spent asking questions about how we can help clients,” writes the London-based Smith, head of the firm’s U.S. equity derivatives business in Europe, the Middle East and Africa.

“It’s purely about how we can make the most possible money off of them. If you were from Mars and sat in on one of these meetings, you would believe that a client’s success or progress was not part of the thought process at all. It makes me ill how callously people talk about ripping their clients off.”

Goldman Sachs, famously raked over the coals by sneering U.S. lawmakers in a congressional hearing two years ago, has become a symbol of the predatory Wall Street practices that triggered the financial meltdown of 2008.

Four years later, the U.S. is still struggling to recover from the ensuing recession. The unemployment rate hovers at about eight per cent and a devastated housing market is only just starting to pick up after a historic, nationwide plunge.

The country’s Securities and Exchange Commission charged Goldman Sachs with fraud two years ago; the 143-year-old company agreed to pay US$550 million to settle charges of misleading buyers of a complex mortgage investment, the largest fine ever paid by a Wall Street firm.

If Smith’s allegations are to be believed, the culture at one of the most powerful firms on Wall Street remains unchanged.

He writes that he’s seen five different managing directors over the past year describe their own clients as “muppets,” sometimes over company e-mail.

“I don’t know of any illegal behaviour,” writes Smith, whose clients have total assets of more than a trillion U.S. dollars.

“But will people push the envelope and pitch lucrative and complicated products to clients even if they are not the simplest investments or the ones most directly aligned with the client’s goals? Absolutely. Every day, in fact.”

Smith, who’s been with Goldman Sachs for 12 years, added: “The firm has veered so far from the place I joined right out of college that I can no longer in good conscience say that I identify with what it stands for.”

He pointed the finger of blame at the firm’s top managers.

“When the history books are written about Goldman Sachs, they may reflect that the current chief executive officer, Lloyd C. Blankfein, and the president, Gary D. Cohn, lost hold of the firm’s culture on their watch,” he wrote.

“I truly believe that this decline in the firm’s moral fibre represents the single most serious threat to its long-run survival.”

Goldman Sachs released a statement in response to Smith’s explosive allegations.

“We disagree with the views expressed, which we don’t think reflect the way we run our business,” the company said.

“In our view, we will only be successful if our clients are successful. This fundamental truth lies at the heart of how we conduct ourselves.”

An editorial on Forbes.com was quick to dismiss the company’s tepid response.

“That can’t be nearly enough,” Frederick E. Allen wrote. “Goldman Sachs must take drastic action to restore its reputation, and that action must start at the top.”

The op-ed swiftly became a trending topic on Twitter, and prompted at least one parody, entitled “Why I Am Leaving The Empire, by Darth Vader.”

“Leadership used to be about ideas, setting an example and killing your former mentor with a light sabre,” reads the parody on TheDailyMash.com. “Today, if you make enough money you will be promoted into a position of influence, even if you have a disturbing lack of faith.”

The op-ed will likely cause embarrassment for both Democrats and Republicans.

The Obama administration has close ties to Goldman Sachs; several treasury and commerce officials, and various advisers, have worked for the investment bank. The firm was also one of the biggest corporate donors to Barack Obama’s 2008 campaign for president.

In 2012, however, Goldman Sachs is one of Republican Mitt Romney’s biggest campaign contributors. Romney has been under fire at times during his campaign for president because of his past as a venture capitalist.

Goldman Sachs took US$10 billion in federal bailout money at the height of the financial crisis. It has since repaid the money, with taxpayers earning $1.4 billion in interest on their investment.

But despite a 47 per cent plummet in earnings and a 26 per cent decrease in revenues in 2011, average pay and bonuses per employee has only fallen by 15 per cent.

On Tuesday, the company agreed to pay US$7 million to resolve claims by federal regulators that it failed to properly supervise commodities trading accounts.