Madonna has appeared to take another swipe at Lady Gaga, saying "imitation is the highest form of flattery".

The singer dedicated her track 'Masterpiece' to the younger star during a performance in Atlantic City, New Jersey, over the weekend, and appeared to accuse her of imitating her.

She told the crowd: "I love her. I love her. I do love her. Imitation is the highest form of flattery."

She then cryptically added: "And one day, very soon, we're gonna be on stage together. Just you wait."

Madonna, 54, has previously accused Gaga, 26, of copying her track 'Express Yourself' on her single 'Born This Way'.

She said: "I thought, 'What a wonderful way to redo my song'. I mean, I recognised the chord changes. I thought it was... interesting."

During her current MDNA tour the star has also been performing a version of 'Express Yourself' which leads into 'Born This Way'.

Gaga has only indirectly adressed Madonna's coments against her, saying she gets upset anyone would make a "mockery" of someone else's work.

Speaking at a concert in New Zealand she said: "It sometimes makes people feel better about themselves to put other people down or make fun of them or maybe make mockery of their work.

"I feel like if you're a really good human being, you can try to find something beautiful in every single person, no matter what.

"I don't even want to fight back, because it's more important to me to keep writing music."