Pop sensation Lady Gaga has taken a swipe at Kelly Osbourne in an 'open letter' post shared today (January 10) via her website LittleMonsters.com.

Written from the point of view of her Body Revolution campaign in association with the Born This Way Foundation, which Gaga created with her mother Cynthia, she publicly asks Osbourne how she transitioned from being the bullied to the bully with her current job as a presenter on the E! show, 'Fashion Police'. 

The 'Judas' songstress says: "I have empathy for you Kelly, but I feel it culturally important to note that you have chosen a less compassionate path."

She goes on to discuss how Osbourne was once the victim of verbal abuse and criticism because of her weight, but questions how she then slimmed down and decided to work in a career where she displays that very same negative behaviour towards other stars:

"Your show breeds negativity, and over the years has even become comedic in nature [...] What about your body revolution? It used to make me truly sad when I would hear people talk about your weight when you were younger, as I was bullied too."

"To see you blossoming into a beautiful slender woman who makes fun of others for a living is astounding. Why not help others?"

Gaga concludes the letter by admitting that she's not making an example out of Osbourne, but just wants to encourage her to be responsible. 

Watch Gaga perform with the Rolling Stones at their recent concert below: