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'."

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