The letter which appeared in Springfield News-Leader also urged all Christians to vote for Mitt Romney in the forthcoming US elections, the Hollywood Reporter said.
The identity of the letter writer caused some confusion as at first the paper had issued a note denying that Jane was related to the Hollywood actor.
However a second note then appeared saying, "To clear up earlier confusion, the News-Leader has verified the letter writer is the mother of actor Brad Pitt and local businessman Doug Pitt."
The letter itself identified Jane as "a Christian who differs with the Mormon religion".
She went on to say that "any Christian should spend much time in prayer before refusing to vote for a family man with high morals, business experience, who is against abortion, and shares Christian conviction concerning homosexuality just because he is a Mormon."
"Any Christian who does not vote or writes in a name is casting a vote for Romney's opponent, Barack Hussein Obama - a man who sat in Jeremiah Wright's church for years, did not hold a public ceremony to mark the National Day of Prayer, and is a liberal who supports the killing of unborn babies and same-sex marriage," she wrote.
Both Pitt and his fiancee Angelina Jolie are Obama supporters and outspoken champions of gay rights.