Legal highs: 'Spice more addictive than crack'
The Chief Inspector of Prisons says so-called legal highs are leading to increased violence and deaths in prisons.
People working with drug addicts are particularly concerned about the rise in the use of "spice".
Radio 1 Newsbeat's Jim Connolly went to meet 29-year-old Dave.
He had spent six years in prison and had been a crack cocaine addict and came across "spice" on his last time in jail.