And it just gets worse in the controversy over Yahoo CEO Scott Thompson and the circumstances around how a fake computer science degree could get onto his bio.

Heidrick & Struggles is smacking back at him for insinuating that the well-known headhunting firm had messed up his resume.

In meetings with employees to attempt to explain the situation yesterday, multiple sources said that Thompson claimed that a mistake made by a headhunting firm in mid-2000, when he was moving to a job at eBay, was the way the inaccuracy got into his bio.

Thompson did not name the firm, but he was clearly referring to Heidrick & Struggles, which handled that placement. It was also working on the Yahoo CEO search, after the Silicon Valley Internet giant fired its former CEO Carol Bartz last fall.

But, because it had originally placed Thompson at eBay, the firm did not work on his hiring at Yahoo.

So, Heidrick was not going to take Thompson’s blame for the botched bio.

“While we were not involved in this placement, there have been both direct and indirect mentions of this relationship in several news articles. Furthermore, if recent media reports are accurate, the CEO of Yahoo! has made potentially damaging allegations about our firm that are simply not true and cannot be allowed to stand in the public record,” wrote CEO Kevin Kelly to staff. “The media articles in question have indicated that the Yahoo! CEO told members of his senior staff that, many years ago, a junior member of our firm invented an academic credential for him in the course of preparing standard profile materials. Based on information in our possession, this allegation is verifiably not true and we have notified Yahoo! to that effect.”

This letter is just another brick in what is looking like an insurmountable wall for Thompson to keep his job at Yahoo. Sources said that the board of Yahoo had been sent a letter from Heidrick on the matter earlier today.

And, let me just say, this latest eruption is simply not good for Thompson’s chances to remain CEO for much longer.

Yahoo declined to comment, but here is the full letter from Kelly to its staff:

Colleagues,

Heidrick & Struggles’ clients across the globe place their trust in our professionalism and discretion, as we assist them in their most significant leadership decisions. We regard that trust as one of our most valuable corporate assets. As such, we do not often comment on internal matters involving our clients. However, recent press accounts have reported statements that contain misstatements of fact and criticisms of our professional services that require a response from us.

As many of you have seen, there has been recent focus on the CEO appointment at one of our long-term clients, Yahoo!. While we were not involved in this placement, there have been both direct and indirect mentions of this relationship in several news articles. Furthermore, if recent media reports are accurate, the CEO of Yahoo! has made potentially damaging allegations about our firm that are simply not true and cannot be allowed to stand in the public record. The media articles in question have indicated that the Yahoo! CEO told members of his senior staff that, many years ago, a junior member of our firm invented an academic credential for him in the course of preparing standard profile materials. Based on information in our possession, this allegation is verifiably not true and we have notified Yahoo! to that effect.

This is why I am writing to you today. All of us at Heidrick & Struggles take our responsibility to our clients very seriously, and it is important for us to set the record straight when our good work and reputation are called into question.

The issue surrounding Yahoo! underscores the importance and impact of the work we do for all of our clients — helping them build the best leadership teams possible. Our clients place their trust in us each day, and we have developed strong policies and procedures over our nearly 60-year history to serve them.

On behalf of the management team and Board of Directors, thank you for your continued support and dedication to Heidrick & Struggles.

Best,
Kevin
L. Kevin Kelly
Chief Executive Officer
Heidrick & Struggles

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In BoomTown’s ongoing quest to overdose on tech conferences, I traveled south of San Francisco last night for Fortune magazine’s Brainstorm: TECH conference.

Run by David Kirkpatrick, it’s well done and a great place to run into a range of techies from Silicon Valley, as well as talk to more creative thinkers on where tech is going.

I was there to be on a dinner panel with fellow bloggers Om Malik of GigaOm and my favorite geek to tease, Robert Scoble, of Scobleizer. Fortune’s Adam Lashinsky moderated.

It was an interesting panel about a range of topics, from Yahoo (YHOO)–Kevin Kelly was bored, bored, bored with that topic–to the looming economic pressure that the digital industry is about to experience (a bummer, but entirely true).

Here’s the video: