An executive director at Goldman Sachs has attacked the "toxic" and "destructive" culture at the investment bank in a devastating resignation letter.

Greg Smith, who resigned from his role as executive director and the firm's United States equity derivatives business in Europe, the Middle East and Africa, resigned from the bank after 12 years with a scathing resignation letter published in the opinion page of the New York Times.

In the article, titled Why I am Leaving Goldman Sachs, Smith explained how he was disgusted at how the company valued making money from its clients instead of trying to help them.

"I can honestly say that the environment now is as toxic and destructive as I have ever seen it."

Smith, whose client base at Goldman Sachs had total assets of more than $1 trillion, said: "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.

"I attend derivatives sales meetings where not one single minute is spent asking questions about how we can help clients. It's purely about how we can make the most possible money off them. If you were an alien 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.

"I have always taken a lot of pride in advising my clients to do what I believe is right for them, even if it means less money for the firm. This view is becoming increasingly unpopular at Goldman Sachs. "

Smith also described how he felt "ill" while he was listening to people openly trying to rip off their clients. At least five managing directors referred to their own clients as "muppets" in his hearing, he said.

Goldman Sachs is one of the most influential investment banks in the world but is shrouded in controversy. It has been blamed for trying to mask the true extent of Greece's financial problems so the country could join the euro.

Smith finished his letter by writing: "People who care only about making money will not sustain this firm - or the trust of its clients - for very much longer."