A Christchurch man being sentenced for the manslaughter of a young father has made an emotional apology to his victim's family.

Twenty-year-old Taele Faletolu pleaded guilty in May to assaulting Alfred Waterhouse outside a New Brighton party in March.

The 20-year-old died in hospital a week later.

Before sentencing got underway at the High Court in Christchurch this morning, Faletolu turned to address the Waterhouse family.

Through tears he told them how deeply sorry he was for leaving two children without a father because of his actions.

"My careless act has caused pain that I can never repair.

"I just want you and your family to know I am so sorry for the suffering I have caused you and your family."