To clear up confusion (I hope) "sacrilegious" is correct. The last three syllables don't represent a form of the word "religion", though it might be tempting to think so.

The parts of the word are "sacri"--referring to sacred things--
and the last part, "-legious" is from "lego", to take.

The combination originally referred to stealing sacred objects.

Hope this clears up the spelling problem.

Dave Oesterreich