John Mayer has taken an underhand dig at Jennifer Aniston's ex-husband Brad Pitt in his latest attempt at comedy.

The singer - whose relationship with Jen is reportedly on shaky ground after a disasterous New Year in Mexico - has recorded a 'motivational pep talk' video by himself - to himself.

In the video, which appears on TMZ, John reflects on his best personal traits and mocks Brad's Oscar-nominated film The Curious Case of Benjamin Button.

John says, "Hi John it's John and this is power tape number 9: Potentialising your dreams.

"Your a man of strength, charisma, girth, honour, girth...and influence.

"You know like that guy in the movie the Curious Case of Benjamin Brat, Benjamin Brat, the older you get, the younger you get and right before you die a little tiny man baby you're gonna discover the ability to time travel into volcanoes.

"I never saw the film, I'm just guestimating that that's how it ends."