Warrants have been issued for the arrest of two child sex offenders after they breached their release conditions, as the Corrections Department says it did the same for 13 other high-risk offenders last year.

Brian Conroy, 43, and Adam Biddle, 39, both convicted of sexual offences against children, are being sought after they breached their extended supervision orders.

Such orders control their activities for up to 10 years after they are released from prison. It is the third time both men have breached their orders and Biddle twice had contact children during his breaches.

Conroy is believed to be living in the Wellington area and Biddle in Hamilton.

Corrections Department figures show 13 arrest warrants were issued after 64 child sex offenders breached their conditions in the year to June 30, Fairfax reports.

Twenty-nine came into contact with children under 16, including seven who were involved in "incidents".

Corrections' probation manager Katrina Casey said the numbers were expected given there were 209 offenders subject to orders, and it actually showed Corrections staff were vigilant.

The numbers reflected the difficult nature of child sex offenders.

However, they also showed staff were not letting them get away with anything.

The department was acting "awfully fast" against Conroy and Biddle, she said.

On Friday, Terito Henry Miki will be sentenced on charges relating to him working as a school teacher, despite having been convicted of child sex offences and being under a supervision order.

The case sparked a ministerial inquiry and led to Corrections Minister Anne Tolley looking into a sex offenders' register.