The operator of Auckland's Mt Eden Correctional Facility admits there's room for improvement after a report released on its performance targets.
SERCO has failed to meet half of its targets for the nine months to April, with incidents including the wrongful release of three inmates, one escape and three wrongful detentions.
Managing director Paul Mahoney says it has delivered on of the lowest positive drugs tests nationwide but acknowledges there needs to be improvement in other areas.
"The plan is to reach a high level of performance - we think that looks like achieving 90 percent of the performance measures by the end of this year."
Mr Mahoney says they have a zero tolerance policy on serious incidents.
"What I want to see over the next quarter is more improving. Certainly we want to see some of the measures like our drug testing and the results we've got in our self-harm area improving."
He says they have plans in place to do better in the next quarter.
"I think it's important to also say that we have improved in a majority of these measures over the quarter. I think that does give us confidence that an improvement will continue."
Corrections deputy chief executive Christine Stevenson is aware there are too many serious assaults at the prison.
"That's not satisfactory and SERCO are aware that we're not at all pleased with their performance there. They're putting in place plans to ensure that they do better and this is something we'll certainly be looking at."
Ms Stevenson says they have set some very tough targets for SERCO to meet.
"SERCO is new to New Zealand, and this is their first year and I think it's quite a hard ask to come up to speed as quickly as perhaps we had hoped they would."
She says the Auckland prison is a very busy and difficult prison to run.
The Public Service Association's questioning the Government's decision to open another private prison in 2015, in light of the results of the report. Private prison operator SERCO will be running the new prison.
PSA National Secretary Richard Wagstaff says he expects more poor results if SERCO runs another prison.
"It's also going to bleed the public system because the Government will be committed to filling the beds in that private prison, and that means the public prison will empty out which are actually doing a better job than the private ones."
Mr Wagstaff says the Corrections Minister Anne Tolley's acceptance of the poor results is extraordinary.
"She seems to have a different standard of expectations for privatised services than she does for public services. I'm sure she wouldn't be saying that about the public sector, well one would hope not.
"I don't think we should accept lower standards for privatised prisons, and I don't think we should be wasting any more money on them."
SERCO was fined $150,000 for the February escape of Aaron "Houdini" Forden.
Photo: Mt Eden prison (Getty Images)