Auckland Prison has apologised to its neighbours at Paremoremo for an overflowing sewer that has caused a stench sporadically for years.
The sewer, owned and operated by the Corrections Department, has caused a stench in nearby Te Araroa Drive several times and has overflowed twice in the past 18 months.
The area is part of Prime Minister John Key's Helensville electorate, and a spokesman confirmed that his office received a complaint about the latest blowout last month and was "in the process of responding".
Corrections Department property director Natasha Possenniskie said: "Corrections is committed to resolving the sewerage issue at Auckland Prison and apologises to nearby residents who have been affected. We are working to fix the problem."
A resident said that at its worst the stench from the sewer was so bad that his family found it impossible to walk in their garden.
"Last year it blew two manhole covers off," he said. "Just before the election they replaced a lot of manhole covers in Te Araroa Drive, but it leaked from the manhole cover again a month ago, and of course sewage then pours out down the road and into the stormwater."
The area does not have a bulk water supply and residents have their own rainwater tanks and septic tanks.
Te Araroa Drive is a steep, bushy area and the sewer runs down through the Lucas Creek Scenic Reserve and under the creek to a pumping station in Greenhithe.
Upper Harbour Local Board member Margaret Miles, also a Paremoremo resident, said she had been lobbying to get the sewer fixed since she was a North Shore city councillor before the Auckland Super City was created in 2010.
"It's been ongoing for years," she said.
Ms Possenniskie said the latest overflow was caused by an electrical fault at the prison's sewerage plant which triggered both pumps into action at full speed.
"This caused a flow of sewage beyond the capacity of the sewerage pipes and resulted in the overflow via the manhole," she said.
"The pumping system was reset shortly on the day of the spill, so the flow of sewage reduced to a capacity the pipes were able to cope with."