Rolling Stones star Keith Richards says he has finally given up drugs - because they are too weak to give him a high.

The group's guitarist has complained that modern drugs lack power, claiming that dealers and chemists have reduced their strength.

The 62-year-old former heroin addict told The Sun that modern drugs such as ecstasy "mess with the brain".

He said: "I really think the quality's gone down. All they do is try and take the high out of everything.

"I don't like the way they're working on the brain area instead of just through the blood system.

"That's why I don't take any of them any more. And you're talking to a person who knows his drugs."

He said the only time he would take drugs is if having a medical proceedure, adding that he asked a nurse for extra morphine when he hit his head after falling from a tree in Fiji in April.

"She was very accommodating," he joked.

Richards is currently on a world tour with the rest of the Rolling Stones.