Few would dispute the similarities between them, but Madonna appears to have taken a direct swipe at Lady Gaga.
In leaked footage that appeared on YouTube the 53-year-old singer performed 'Express Yourself' during rehearsals for her 'MDNA' tour in Israel before launching into Gaga's 'Born This Way', a song which has often been accused of being similar to Madonna’s .
She then seemed to confirm that she was took a pop at her younger rival by singing 'She's Not Me' from her 2008 album 'Hard Candy', in leaked video footage which has appeared on YouTube.
This isn't the first time Madonna has referenced the similarities between the two songs.
She has previously said: "I thought, 'What a wonderful way to redo my song'. I mean, I recognised the chord changes. I thought it was... interesting."
Other musicians have also weighed in on the debate with Noel Gallagher calling Gaga - who is currently on her 'Born This Way Ball' world tour - "Madonna-lite".
He said: "I don't give a f***ing monkey's about Lady Gaga. It's all about the meat suit and the controversy. Is it about music? Really? She's got the publicity side sorted, but where's the f***ing music.
"Her album gets played a lot around my house by my daughter and it's Madonna-lite. Madonna was hardcore. She took it to the edge musically as well as everything else.
