California's $1-billion investment in drug treatment for prisoners since 1989 has been "a complete waste of money," the state's inspector general said Wednesday, and has done nothing to reduce the number of inmates cycling in and out of custody.

One study of the two largest in-prison programs found that recidivism rates for inmates who participated were actually a bit higher than those of a group of convicts who did not receive treatment, Inspector General Matt Cate said.

He said corrections officials were told in more than 20 reports since 1997 that the programs were failing but did nothing to fix them, choosing instead to expand them and fund more studies of their results.