EBay is suing Amazon, claiming the Seattle-based retailer infiltrated its email system with the intent to poach its top sellers.

The lawsuit alleges the scheme began in 2015, when it claims Amazon representatives began setting up eBay accounts to access eBay's "member to member" (M2M) email system. That allowed Amazon representatives to contact hundreds of eBay sellers, asking them to switch to Amazon, according to the lawsuit.

EBay noted that such behavior violates its policies, which "prohibit eBay members from using the M2M system to solicit people to sell off the platform." Its rules also bar members from exchanging personal information, such as phone numbers, over the platform.

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Amazon representatives allegedly urged the eBay sellers to contact them off the platform, with one writing to a merchant, "they don't exactly like us poking around. Honestly the easiest way to communicate about this would be on the phone."

EBay described the alleged behavior as "an orchestrated, coordinated, worldwide campaign."

While eBay started out as an online auction site, about 80 percent of its 1.1 billion listed items are now new. Amazon, meanwhile, has added more third-party sellers, who also sell new items and are competing with eBay merchants for customers.

Amazon declined to comment.