Origin will be required to run all editions of Mass Effect 3 on PC, BioWare has revealed - including copies bought from shops.

Mass Effect 3 won't be available on Steam.

"During initial release, Mass Effect 3 will be available on Origin and a number of other third-party digital retailers, but not on Steam at this time," wrote community man Chris Priestly on the BioWare forum.

"Steam has adopted a set of restrictive terms of service which limit how developers interact with customers to deliver patches and other downloadable content. We are intent on providing Mass Effect to players with the best possible experience no matter where they purchase or play their game, and are happy to partner with any download service that does not restrict our ability to connect directly with our consumers."

It's a similar line to the one EA used when defending the removal of Crysis 2 and Dragon Age 2 from Steam.

Mass Effect 3 on PC will require one-time online authentication before the single-player game can be played. Multiplayer Mass Effect 3 will obviously require a constant internet connection.

There will be no limit to Mass Effect 3 game installations.

Priestly stressed that Origin is not spyware and will not gather information against your will.

"Origin is not spyware," he wrote, "and does not use or install spyware on user's machines.

"In order to allow Origin to install games and their patches for everyone to use, Origin implements a permission change that results in Windows, not Origin, reviewing the file names in the Program data/Origin folder. This is an ordinary Windows function, not an information-gathering process. "