In the past 16 months, 25 full-time equivalent positions (FTEs) have been added to the council's ranks.
Council people and culture group manager Lisa Baillie said the increase was "due to a number of contributing factors".
The council was "reducing reliance" on contractors and consultants.
"We are also experiencing significant growth in activity within the district, both in volume and scale/complexity of some of these developments," she wrote in a Local Government Official Information and Meetings Act response to an Otago Daily Times request for an update on staff numbers.
"We are working hard on improving the effectiveness and efficiency of our systems, including our information technology and information system service delivery. And we are experiencing increased legislative and policy demands placed upon local authorities by central government across a wide range of our functions, from building control to planning etc."
In March last year, the council started looking for additional space after a report from council assets group manager Neil Jorgensen said crowding at the council's Thames St headquarters - fitting 122 staff into the building - was a "somewhat urgent" issue.
In July last year, the ODT reported the council spent $350,000 on the 1882 grocery store next door to its headquarters to deal with overcrowding for the medium to long term.
However, earlier that year the council's parks and property teams moved into refurbished office space above Cucina restaurant at the corner of Tees and Itchen Sts as a short-term solution.
A council spokeswoman said 17.3 FTE or 22 people used that space at present.
Mrs Baillie said that at the end of June 2018, the council employed 139 FTE, 135 permanent and 4 fixed-term employees; by June 2019 that rose to 152 FTE, 145 permanent and 7 fixed-term employees; and at Sept 9, 2019, the council employed 158 FTE, 146 permanent and 12 fixed-term employees.
She said the delay in her response to the ODT was due to inaccurate information in the "ratepayer's report" produced by the New Zealand Taxpayer's Union.
Waitaki Mayor Gary Kircher criticised that report, which said the council had the fourth-highest personnel cost per household in the country.
The report, which is based on figures from the 2017-18 year, uses a raft of mostly financial measures to compare 66 of the country's local authorities, but incorrectly stated the council had 106 staff, 21 of whom earned more than $100,000.
Taxpayers' Union spokesman Louis Houlbrooke said the report looked at staffing costs per household, to compare how "bloated each council's bureaucracy is on an apples-to-apples basis".
The better comparison in Waitaki's case was the personnel costs for the council, excluding council-controlled organisations, Mr Kircher said,
That comparison has Waitaki at $1127 per household and 21st out of the 67 councils compared.
Data for the report was supplied to all councils for review before publication, a statement from the Taxpayers' Union said.
Mrs Baillie said the council was working with the Taxpayers' Union to correct the information it used.
