In it, eBay said that Amazon representatives abused eBay's internal email system to contact sellers - a violation of the marketplace's policies.
The lawsuit, recently filed in Santa Clara County, California further stated that Amazon was aware that its practices violated eBay's use policies and said the activity was "part of a larger pattern of aggressive, unscrupulous conduct."
Amazon representatives reportedly sent hundreds of emails in 2015, only recently did eBay find this out, it said.
eBay wrote: "eBay brings this action because Amazon — unwilling to fairly compete for third-party seller business — instead has resorted to an orchestrated, coordinated, worldwide campaign, using eBay’s proprietary M2M system, to illegally lure eBay sellers to sell on Amazon.
"eBay seeks to stop Amazon’s unlawful scheme and to obtain redress for the damage it has caused.”