A prisoner who plotted to have Justin Bieber kidnapped, castrated and then killed has revealed that he still wants to carry out his attack.

Dana Martin, who is currently serving two life sentences in the US for raping and killing a 15-year-old girl, recently hit the headlines again after telling a prison guard about the project.

It is said he wanted to hire two men to castrate the singer with pruning shears at New York's Madison Square Garden - before paying the hitmen $2,500 for each testicle.

Speaking to Details magazine from his cell, Martin - who is being investigated over his plans to slay the 'Believe' singer - said that the murder plot is still on his mind. He said:

"It's still on. This isn't going away. Do you really think that I would stop?"

Revealing why he wants to attack the Canadian, Martin added: "It's because he changed, that made me angry."

The inmate also showed the magazine a tattoo of Bieber he has on his calf, saying:

"I shaved it for you...I always tell people you need to have a shaved Bieber. Believe me, you do not want a hairy Bieber."