Crooked prison guards have been smuggling contraband to inmates, with seven losing their jobs in three years.
Corrections Department figures show more than 6000 banned items were seized coming into prisons in the 11 months to May 30 this year.
Some banned items made their way into prisons with the help of Corrections staff, with 13 staff disciplined for smuggling for the three years to December 2011.
Of these, five received only written warnings, while seven were sacked. Another staff member resigned.
Corrections services assistance general manager Maria McDonald said most staff were very professional but a few had "let the side down".
Changes had been made recently to improve staff "integrity", including drug testing and credit checks for staff with financial responsibilities, she said.
The department has refused to release details of the smuggling but some guards were charged with corruption, and possession or supply of contraband.
In June last year, Rimutaka prison guard Johan Edwin Clarke was sentenced to two years and three months in prison for corruption.
Clarke admitted accepting $2850, sex with prostitutes and expensive wine in return for smuggling drugs, cigarettes and even dental floss.
Another guard admitted smuggling tobacco for an inmate who was an old friend.
Drugs that are not smuggled by staff are sometimes thrown over roadside prison fences, in what is known as a "throw-over", and in other instances snuck in by visitors.
Figures show contraband seizures are rising, with another 1401 in the 11 months to June compared to the previous year.
Corrections said the jump corresponded to an increased effort to smuggle tobacco, which was banned in prisons in July last year. With the exception of tobacco, drugs were the most commonly seized product, with more than 3400 intercepts since December 2009.
The biggest contraband hauls have been pulled out of Rimutaka and Christchurch prisons.
At Rimutaka Prison, drugs were seized on 116 occasions in the past year.
More than 120 communication devices, mostly cellphones, were also seized, along with 92 tattooing tools.
McDonald said many seemingly harmless household items were also banned in prisons because they could be adapted to illegal uses. "Even sugar may be contraband in prisons if stockpiled, as it could be used for homebrew," she said.
Other items banned include honey, fruit juice and electric toothbrushes.