Image as plane affecting object in front

Hello!

I am only one month into Blender and I can’t seem to find the right Google results for my issue.
I have created three bottles in a scene and have added an image as plane, to act as a static background.
Despite have an IsCamera Ray node as suggested by a search result, the Emission image plane is still affecting the three bottles in front of it.
When I hide the plane the coloured liquids are brighter, as they should be - when I show it in the scene the liquids darken somewhat…

I need the background plane to not affect anything in the scene at all, merely act as a background image. Then my external/world lighting can do the rest.

Any suggestion would be much appreciated!
Many thanks
Simon

Show your node setup or post a link to your blend file, you probably have the Light Path node connected wrong.