Antonym of "Gospel Truth"
What would be the antonym of the phrase "Gospel Truth" be?
Consider the usage in the sentence: "Don't consider articles in the newspaper as the gospel truth" what would the opposite be?
Specifically I'm looking for some sort of evangelical/biblical references which would depict falsehood.
The antonym of "gospel truth" would be "utter falsehood", or if you wanted a colloquialism, "bullsh*t." From your example it seems you don't want an antonym, but an alternative. That is "don't consider articles in a newspaper gospel truth, instead -blank-." For that, I'd suggest the idiom "take with a grain of salt."
If you're after something with a biblical flavour, how about "heresy"? Wiktionary definition:
A doctrine held by a member of a religion at variance with established religious beliefs, especially dissension from Roman Catholic dogma.
A controversial or unorthodox opinion held by a member of a group, as in politics, philosophy or science.
It is "Fiendish Lie."
I take it you're trying to pair off Biblical allusions, "Gospel truth" versus something-Biblical-sounding.
My first thought would be "diabolical lie". "Diabolical" comes from the Latin word for devil, so that would have some theological "feel". And it's a phrase used often enough that you wouldn't have to explain it. (I'm assuming here that by opposite of "Gospel truth" you mean an extreme lie, as opposed to a questionable truth.)
There are plenty of cases in the Bible of people lying: Ananias and Sapphira lying about their generosity, Potiphar's wife making false rape allegations, Abram claiming that Sarai was his sister, Samson and Delilah lying to each other about the source of his strength and why she wanted to know, etc etc. (Pause here to allow atheists to interject that it's all a pack of lies.) I don't know of any stock phrases alluding to such incidents, though. You could always spin a phrase, "You can't trust Mr Jones boasts about his charitable contributions any more than you could trust Ananias" or something like that. If you're looking to be readily understood, such an allusion would simply confuse anyone not familiar with the Bible story. But if you're trying to make more colorful writing, it might be workable.
A biblically flavored antonym for "gospel truth" would be "speaking with a forked tongue".
This post in Foreign Policy Journal, "The U.S. is Speaking with Forked Tongue" cites an exclusively Native American origin. However, there is an association with deceit from the passage about the Garden of Eden in the Book of Genesis. The serpent speaks with a forked tongue to Eve, and that is what gives the expression "speaking with a forked tongue" the powerful connotation of falsehood. This provides the full passage from the Book of Genesis that refers specifically to Adam and Eve and the snake.
Both PsychCentral (secular website), and Spirit Community on Christian Dream Interpretation (non-secular website in a pantheist sort of way) attribute dreams about snakes and speaking with forked tongue to the biblical snake whose lies were Eve, and Adam's, undoing in the Garden of Eden.
EDIT
Additional detail from source PsychCentral about "forked tongue and deceit" as the opposite of Gospel Truth:
Snakes are associated with transition and evil because of their Biblical heritage. A snake encouraged Eve to eat fruit from the Tree of Life in the Garden of Eden — which subsequently provoked the proverbial “fall of man.” Snakes... are associated with lying and betrayal, because they have a forked tongue.
It is easy to see the link between the act you committed and symbolic meanings of treachery and deceit. Because you betrayed a friend, you probably feel like a “snake in the grass.” And yes, you told lies, which means you were speaking with a “forked tongue.”