Just days before publication of a book promising to expose a rampant culture of greed at Goldman Sachs Group Inc (GS.N), the Wall Street company is writing its own story about the book's author.

Greg Smith, a former Goldman salesman whose tell-all book is due out next week, demanded a big raise and a promotion last December, and left the firm a few months after not receiving either, a Goldman Sachs source said.

The bank has conducted an investigation of Smith and found that from 2007 onward, he received performance ratings in the bottom half of the company's scale, the source said. Those low scores are particularly damning because Smith picked the reviewers himself, the source added.

A spokesman at Grand Central Publishing, which will officially publish the book on October 22, said Smith will not be available for comment until then.

Smith worked at Goldman for more than 10 years, and left soon after submitting an opinion piece to the New York Times that said the bank was a "toxic" place, where managing directors referred to their clients as "muppets."

At a meeting with a manager in December 2011, Smith demanded to be paid more than $1 million and sought a promotion from vice president to managing director, the source said.

"Greg Smith off the charts unrealistic, thinks he shld sic trade at multiples," the manager wrote in an email about the interview, according to the source. "We told him there's very little tolerance for reactions like that and he needs to tone it down."