Matt Koppenheffer

Conspiracy theorists, gather in close, you're going to love this.

We know that the LIBOR bid-rigging scandal that's battering Barclays (NYSE: BCS) is a big deal. The bank was hit with massive fines after it was found that traders at the bank were pushing fudged bids to the British Bankers Association's LIBOR calculation. In many cases, those rigged bids were aimed at benefitting Barclays' trading positions.

After fighting tooth and nail against it, Barclays' CEO Bob Diamond got axed in the wake of the revelations. But, in preparation for testimony in front of a British parliamentary committee, Diamond dropped a bomb.

Back in 2008, Diamond had a chat with Paul Tucker of the Bank of England -- the U.K.'s version of the Federal Reserve. According to Diamond in his testimony, as well as in an email from 2008, the conversation went something like this:

Tucker: Hey Bob, Barclay's submissions for LIBOR have been high, and that doesn't really look good since it makes people think Barclay's is in worse shape than other banks.

Diamond: Well, Paul, what do you want us to do? Those are the rates we'd have to pay. We're just being realistic.

Tucker: I guess you have to pay what you have to pay.

Diamond: Exactly. And get this -- we're not in any worse shape than any of those other banks, and we have a pretty good idea of what they have to pay, and it's not as low as what they're submitting.

Tucker: I'm not trying to run your bank, Bob, but I will tell you that the calls I'm getting are from senior levels in Whitehall. Take this for what it's worth, but maybe you don't have to be at the high end all of the time.

So I took a bit of artistic license with that exchange, but the bottom line is that, in Diamond's version of the story, Tucker was calling to suggest that Barclays put in artificially low bids to make it look like it could get funding at the levels that other banks were claiming at the time.

Obviously, this isn't the last we'll hear on this. Tucker certainly will have a version of the story, and I have a feeling that it won't revolve around him telling Diamond to give false LIBOR bids.

But the suggestion that the BoE and Whitehall were forcing Barclays’ hand in manipulating interest rate submissions wasn't the only bombshell in Diamond's claim. His suggestion that Barclays was coming in towards the high end, because other banks were submitting artificially low bids at the time, would have us believe that … well, Barclays was far fr om the only bank getting silly with LIBOR.

There are 18 banks that submit LIBOR numbers for the U.S. dollar version of the interest rate. Besides Barclays, that group includes Citibank (NYSE: C), JPMorgan Chase (NYSE: JPM), Bank of America (NYSE: BAC), and UBS (NYSE: UBS). Anyone want to wager on investigators finding fishy LIBOR submissions from other banks?

Keep up to date on the fallout by adding Barclays to your watchlist. While you're at it, go ahead and add the other banks as well:

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.