A "league table" for prisons has been made public by the Government.
Rankings for last year have been published for the first time and show Whanganui Prison was the only jail classed as exceptional in September. By December it had lost the top spot and is listed as "exceeding".
At the bottom of the table are Hawke's Bay, Northland and Otago prisons, which "need improvement".
Corrections Minister Anne Tolley released the rankings for the year to September 2012 and the year to last December.
All 17 prisons are measured on their performance in security, assaults, drug tests and rehabilitation programmes.
There are four grades - exceptional, exceeding, effective and needs improvement. More than half of the prisons fall into the effective category.
"These first-ever performance tables are a valuable tool for Corrections and also allow communities to measure how well our prisons are operating," Tolley said.
She said the privately run Mt Eden prison was in the exceeding category, which "shows how much progress has been made by Serco".
Serco was fined $150,000 after an inmate escaped in February, a further $25,000 for releasing an inmate early and $50,000 for failing to file progress reports.
The reports will be released quarterly.
Corrections national commissioner, Corrections Services, Brendan Anstiss said most prisons were operating "effectively or better".
"These results are very good," he said.
"We haven't had a single escape, walkaway or unnatural death in all the periods reviewed."
Otago, Hawke's Bay and Northland staff were working on reducing the number of assaults on staff and prisoners, he said.
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