There's been a big increase in the number of prisoners gaining trade qualifications through training behind the wire.

Figures released by Corrections Minister Anne Tolley show 4767 prisoners passed their trade tests in the last financial year, a 45 per cent increase on the previous year.

"These figures are extremely encouraging - we know that offenders who gain employment after release are less likely to reoffend," she said.

There are plans to boost the numbers further, with new training workshops at Christchurch Men's Prison handling 130 inmates a year.