Kevin Federline: That penis pic is bogus, my real dong's hella bigger

According to reports on TMZ's website, Kevin Federline is calling BS on the naked pic supposedly featuring his legendary baby maker telling people the shot is faker than his rap career.

The shot's been all over the Internet...apparently showing K-Fed gripping his Sexcalibur like he's preparing for battle. 

But sources close to Federleezy say he's 100% certain it's a Photoshopped pic ... not only because he has tattoos down by the dragon's den which aren't in the pic but he also claims his shlong is way shlonger in real life.

K-Fed's penis couldn't be reached for comment.