Cher. REUTERS/Danny Moloshok

Cher has upset leading Mormons by using a derogatory term in a Twitter.com attack on U.S. presidential hopeful Mitt Romney.

The pop superstar, who is a fervent Democrat, sent out a tweet on Friday, urging President Barack Obama and his aides to get organised or risk losing November's election to Republican Romney, who is a Mormon.

Cher wrote, "I Feel if he (Obama) doesn't get all his DUCKS IN A ROW we'll b forced 2 listen 2Uncaring Richy Rich! The whitest man in MAGIC UNDERWEAR in the WH (White House)."

Her remarks have upset prominent members of the Mormon church, who wear formal garments known as "celestial underwear." The term "magic underwear" is considered offensive.

Mormons took to Twitter.com in droves to take aim at Cher, with one calling her an "anti-Mormon bigot", and another stating, "I guess she is another example of a celebrity who surrounds themselves with people who always tell them what they want to hear so that they don't have to think before they speak or tweet in this case."