UPDATED 12.22PM: Stewart Murray Wilson is putting up a fight, as his 21-year jail sentence is extended a year before its due to end.

The convicted sex offender will appeal a six-month sentence he's received for breaking his parole conditions by phoning a woman he was forbidden from contacting.

The judge told the court the circumstances around the call, show he's manipulative and deceitful.

Wilson had previously told the woman he wanted to rip off his bracelet and escape to Australia with her.

In letter Wilson passed to media in the Whanganui District Court, he says it doesn't make sense he could talk to the woman in prison, but not on parole.