A disgruntled former friend and bandmate of country music superstar Tim McGraw plans on publishing a memoir detailing the singer's homoerotic hijinks, including a photo in which he's slapping another man's bare bottom.

McGraw, an insider tells this week's edition of the National ENQUIRER, is indeed a prankster whose ribs can border on risque, but that's not an indictment on the singer's sexuality (as he's married to fellow country star Faith Hill).

The aforementioned photo, which shows the 46-year-old singer with his hand on the man's derriere, was taken during a concert in Milwaukee, after "Tim dared his drummer Billy Mason to