UPDATED 8.17pm Most recent numbers show prison deaths are up, but those responsible for running the country's jails maintain the overall rate of unnatural deaths are actually falling.

Data published by the Department of Corrections shows there were 11 unnatural deaths -- 10 suicides and one from concealing drugs internally-- in jails last year, up from eight the previous year. While self-harm/ threat to life incidents jumped from four to 26 over the same period.

It's the highest number of deaths recorded the past five years.

Labour MP Kelvin Davis said he finds the jump in prisoner deaths, and particularly self harm incidents, "really alarming."

"A lot of it comes down to raising awareness of the violence going on in prisons. Just the conditions in prisons in general. To have a jump from four self harms in one year to 26 the next is just totally unacceptable."

Mr Davis said the fact three out of the 10 suicides happened at Mount Eden Prison indicates problems there aren't all cured.

"There's 18 prisons and three of the suicides happened in one prison. There's still a lot of work to be done there."

Green MP David Clendon sees it as an indicator the prison's been mismanaged, but also of systemic problems.

"We're not managing them well and we're not investing in solutions. We're simply investing in containment."

The Corrections Department says it has programs in place and uses mental health screening to identify at risk inmates, particularly the over 60 per cent with mental health or substance abuse problems.

But Mr Clendon said around 18,000 people entered the prison system last year, and on the department's ratio around 10,000 of them would have met that profile.

"There is clearly not capacity in the prison system, or indeed in the community, to properly deal with those people so that's where we need to put some investment."

However Corrections Department director of prison health, Bronwyn Donaldson said they take such incidents seriously and are committed to preventing and reducing them.

She said processes ensure many prisoners are prevented from self-harming or attempting suicide, and the numbers are steadily declining.

Ms Donaldson said Corrections staff have saved the lives of 60 prisoners over the past five years, and more than 200 over the past 10 years, where the individual would have been unlikely to survive without staff help.