In March, former Goldman executive Greg Smith used the New York Times OpEd pages to resign in spectacular fashion, bemoaning a culture that meant staff only "care only about making money".

Smith wrote that "it makes me ill how callously people talk about ripping their clients off," adding that "over the last 12 months I have seen five different managing directors refer to their own clients as "muppets," sometimes over internal e-mail".

Facing a barrage of negative publicity, Goldman chief Lloyd Blankfein insisted that Smith's claims were being taken seriously and ordered an enquiry, with all internal e-mails scanned in search of derogatory remarks about clients.

Yet according to the FT, the review has found little to back up Smith's claims. The trawl of millions of e-mails found around 4000 'muppet' references but 99% of these related to the film of the same name.

A single message was found that called clients as muppets, with a salesperson writing: "The muppets don't understand they can trade the futures through a block with other liquidity providers."

The investigation's results have found their way to the FT as Smith prepares to publish a book, called Why I Left Goldman Sachs: A Wall Street Story, later this month.

As it prepares for a rash of new revelations, Goldman has let slip that the author complained about his bonus and argued that he deserved to be paid more than $1 million just weeks before his spectacular resignation.