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(Pocket-lint) - Kindle case manufacturer M-Edge has filed a lawsuit against Amazon.com, claiming that the online retail giant threatened to unlawfully "de-list" its products and attempted to change the terms on a three-year contract signed in 2009 through a campaign of "coporate bullying".

M-Edge Accessories, which sells cases for all forms of Kindle, other e-book readers, iPads and the Samsung Galaxy Tab range, filed the suit last Thursday in a Maryland federal court in the US. It states that Amazon demanded an increased commission - to 25 per cent - on its cases sold through the Kindle Store, even though the existing contract equated to 15 per cent. It also claims that Amazon wanted a large lump sum paid retrospectively for cases sold from January 2010:

"In February of 2010, Amazon’s [Jay] Marine called M-Edge and stated that despite the existing contract terms, M-Edge had to retroactively pay the difference between the 8 per cent fee and the 25 per cent fee for all of January, 2010," states the lawsuit. "That amount was approximately $600,000; a sizable sum to M-Edge. M-Edge refused, pointing to its existing, three-year contract which it had just signed in November of 2009. Marine replied that Amazon was “disappointed”, and stated that there would be “ramifications” resulting from M-Edge’s refusal."

Those "ramifications", according to M-Edge, included continuous harassment by Amazon executives Marine and Sara Otepka, with the latter allegedly threatening that "Amazon would 'play' with M-Edge's Amazon.com product pages in such a way that 'no one will be able to find you'."

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When asked about the case by the Wall Street Journal, Amazon declined to respond, stating that, "the company doesn't comment on pending litigation."

Writing by Rik Henderson.