Actually I tried that thanks, but as I expected, the backdrop colour changes when there are no other objects in the scene.

 

Quote - > Quote - Can anyone please tell me a way to prevent objects receiving shadows in Poser 8?

I don't know how to do it in Poser, but you might be able to cheat. Render two versions of the scene. One version with everything except the item you don't want shadows for, and another version with only the item you don't want shadows for. Save them in a format that supports an alpha channel, like PNG, then compose the two parts as layers in a paint application.