A man at the centre of a plot to murder Justin Bieber says his plan is ''still on''.

Dana Martin - who is serving two life sentences for raping and killing a 15-year-old girl - conspired with a hit man to kidnap and castrate the singer, but the star was spared after he let slip his intentions to a prison warden.

However, Dana has vowed to continue targetting the 'Never Say Never' hitmaker, saying: ''It's still on. This isn't going away. Do you really think that I would stop?''

Martin - who is currently in solitary confinement while his repeated threats against the star are investigated - says he targeted Justin because he ''changed''.

He told Details magazine: ''It's because he changed, that made me angry.''

During the interview, the inmate showed off a tattoo he has of 19-year-old Justin on his calf.

He said: ''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.''

Phone calls of Martin discussing details of the murder plot with his accomplices were recently made public.

The plan was to strike in New York when Justin was performing at Madison Square Garden venue and strangle the teen idol with a paisley tie, but only after removing his genitals with garden shears.