Light with halo different with BG

Hi there, I've been trying to sort this out. The pictures will illustrate clearly I think.

I have a point light with a halo and I have the effect I want without a BG. But once I turn on the BG (Which is just a sprite on the "Background" sorting layer it loses it's luster.

Any help would be fantastic as I'm rather stuck.

Thank you in advance, Chris