Katy Perry has lifted the lid on Rihanna's apparent drug habits, suggesting that she is very much a regular user of marijuana.

The 'Stay' star has been pictured smoking the drug and she often makes reference to it via her Twitter account and her clothing.

Speaking to the Canadian Elle, Katy Perry revealed her surprise at how her friend Rihanna looks despite her frequent drug use. She said:

"I think that Rihanna always looks so fresh and I’m like, ‘How do you do that? We all know how much pot you smoke! And you don’t sleep because you’re on Instagram at four o’clock in the morning!'."

Katy Perry meanwhile is due to release her new album 'Prism' on October 22.