Microsoft has lost one of the earliest adopters of its Passport web security technology after eBay decided to dump the protection for its users.
Passport was launched in 1999, and allows users to store passwords and credit card details for use across different websites. EBay had allowed users to use Passport from around 2001.
Passport has caused privacy and security concerns among some users, and some website owners have been fearful of allowing Microsoft to control their customers by storing their personal details.
EBay said few users are using Passport to sign into its site.
In a statement to its users, eBay said, "In late January, we will no longer support the ability for members to sign into eBay through Microsoft Passport. This means that members currently using this service will have to sign in through eBay directly.
"As part of this change, we will also discontinue sending eBay notifications through Microsoft .net alerts."
Passport has an estimated 200 million users, but most use it to sign into e-mail and instant messaging accounts that are part of Microsoft’s MSN Network.
In 2001 the Liberty Alliance, initially supported by Sun Microsystems and 30 other companies, set out to create an open authentication platform as a rival to Microsoft's proprietary Passport technology.