Wellington City Council has admitted its parking contractor accidentally leaked personal details of tens of thousands of motorists to a member of the public who made an official information request.
It says contractor Tenix Solutions sent the man information relating to 120,000 tickets, including names and addresses of vehicle owners and number plates.
The man was sent the information between August and November this year.
Council chief executive Kevin Lavery said the recipient told the council about the breach on 19 November and returned the information.
Mr Lavery described the performance of Tenix Solutions as woeful and said there will be a full review.
Council chief operating officer Greg Orchard apologised for the breach. He said contractors are meant to notify it of information requests but Tenix did not do this.
Mr Orchard said the recipient has assured him he has not kept any data or passed it on. He has asked Tenix to undertake a full review.