Auckland Council had more than 800 complaints of dog attacks on people last year and is looking at tougher penalties for their owners, including disqualification and prosecution.
A quarter of the dogs in attacks were unregistered, said council planning, policies and bylaws manager Andrew Pickering.
He said the council had a number of ways it could address the problem in a review of the seven councils' dog policies and bylaws inherited by the Super City. These included the dog being seized or destroyed.
The owner could also be classified as probationary or disqualified, fined or prosecuted. Where a person was seriously injured the owner could even face prison.
Mr Pickering said dog control officers estimated that 11,000 dogs, or 10 per cent of the city's dog population, were unregistered.