NEW York mayor Michael Bloomberg, who made his early millions on Wall Street before turning them into billions at his own financial data and news company, threw his support behind Goldman Sachs on Friday, after it suffered a blow last week in the form of a scathing resignation letter.

Calling Goldman Sachs "a great firm", Mr Bloomberg used a radio talk show to accuse critics of unfairly "piling on" the bank and said the South African-born former staffer, Greg Smith, was wrong to air his views in the op-ed piece.

"I thought (it was) a nasty letter from an employee," said Mr Bloomberg, who regards loyalty as non-negotiable. It was the second day Mr Bloomberg stood behind Goldman Sachs. He visited the bank on Thursday to express support to its employees. "You know, you go to work for a company, it seems to me they have an obligation to never diss you. They can part company with you. But they should never do that," said the mayor.

Mr Smith, who worked in equity derivatives, said in the op-ed that Goldman had become "as toxic and destructive as I have ever seen it" and was a place he no longer wished to work. "It makes me ill how callously people talk about ripping their clients off. Over the last 12 months I have seen five different managing directors refer to their own clients as 'muppets'," Mr Smith wrote, using a slang term for a stupid person.

The New York Times defended its decision to run the letter.

"It's an op-ed piece," said spokeswoman Eileen Murphy. "It's someone's opinion. The purpose of an op-ed page is it's a forum for people to write their opinion."

She said the letter went through "the same process as any unsolicited op-ed would go through," although she declined to give details of the vetting procedure.

- Goldman Sachs Group's directors must investigate a former employee's allegations about a change in the firm's culture, Jacki Zehner, who was a partner when she left the firm in 2002, wrote on her blog.

Ms Zehner, who worked at Goldman Sachs for 14 years, wrote that she had heard from "many people" in the past few years that the firm is emphasising profits over character. She said she does not know Smith.

"These are very serious accusations from a credible person in my view and I hope it does indeed provide a 'wake-up' call to the board of directors," wrote Ms Zehner, who was the first female trader promoted to partner and is married to a former partner. She is now CEO and president of Women Moving Millions, a non-profit organisation supporting the advancement of women and girls worldwide.

Bloomberg, Reuters