An executive with investment bank Goldman Sachs has published a scathing resignation letter in a major US newspaper.
Greg Smith told the New York Times the environment at the giant global firm is toxic and destructive.
"It makes me ill how callously people talk about ripping their clients off," he said.
Mr Smith, who worked in equity derivatives, said managing directors openly referred to their own clients as "muppets" - slang in Britain for a stupid person.
In a statement, Goldman Sachs said the investment bank said it disagreed with the views expressed, which it does not think reflects the way it runs its business.
"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."
According to the British Financial Services Authority's register, Mr Smith joined Goldman's UK unit a year ago.
Born in South Africa, he attended universities in his home country and in the United States, where, on graduating from Stanford University in 2001, he landed a job at Goldman as a financial stock analyst.
He most recently worked a vice president for Goldman Sachs Services Ltd.
It was the latest blow for the Wall Street investment bank, which in recent years has faced a series of high-profile incidents damaging to its image after the near-collapse of the global banking system in 2008.
Earlier this month it was accused of a major conflict of interest for advising El Paso Corp on its sale to Kinder Morgan, while being a significant shareholder in Kinder Morgan.
One of its bankers, Fabrice Tourre, is still embroiled in legal claims in the United States after allegations that he duped buyers of a complex credit instrument.
And two years ago, chief executive Lloyd Blankfein caused a media storm when he said that as a banker he was just "doing God's work," defending high banker pay and the role their institutions play in the economy.