A violent thug who beat five young Aucklanders during a week-long rampage was on probation at the time.

New details of the 2008 bashings emerged during Ruaumoko Taiapa's appeal against his conviction and 14-year prison sentence.

Taiapa was in a group of four who embarked on a vicious spree on Auckland's North Shore in January three years ago.

They beat two young couples about the head with metal bars, causing severe head injuries.

In dismissing the appeal, Court of Appeal Justice Lynton Stevens said Taiapa had bashed another Auckland woman in the head with a baseball bat only five days earlier. She was hospitalised with a 5cm laceration.

Taiapa should not have been in Auckland because of strict parole conditions after assaulting police.

Taiapa, who has Mongrel Mob affiliations, will not be eligible for parole until 2017.