Serco outperforms most public jails in comparison tables released in bid for greater transparency.

Privately managed Mt Eden prison has exceeded its targets in several areas. Photo / Dean Purcell

Private prison operator Serco is outperforming most public prisons in league tables which measure prison escapes, positive drug tests and rates of violence and rehabilitation.

The Corrections Department published the performance grades for New Zealand's 17 prisons for the first time in a bid for greater transparency and accountability.