Public health officials are denying Prime Minister Jacinda Ardern's claim human waste breached the walls of south Auckland's Middlemore Hospital.

But the Prime Minister is refusing to back down, with her office on Wednesday issuing a statement saying the comment is in line with remarks by Counties Manukau District Health Board's former acting chief executive.

Ardern, while delivering her first statement of the parliamentary year, referred to "sewage down walls", in what appeared to be a reference to widely-publicised issues with Middlemore Hospital's buildings.

CMDHB, which in 2019 said such claims were untrue, has now responded to the prime minister's statement.

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"Despite the dramatic language used previously around sewage issues at Middlemore Hospital, the sewage leaks were small," a spokeswoman said.

She confirmed one incident in the Scott Building in November 2017, but said it was the result of a cracked sewer pipe joiner.

Pipe joinery also required replacement in one of Middlemore's retail areas in October 2017.

However, there was "no sewage spilling into the building" and leaks were "immediately repaired", CMDHB's spokeswoman said.

On Tuesday, Ardern's office said her comments originated from CMDHB itself, pointing to a March 2018 Radio New Zealand interview with former acting chief executive Dr Gloria Johnson.

Johnson said in that interview the DHB "certainly had problems" with sewage leaking at the Scott building.

"And that's another problem that we think a number of buildings could have and certainly not confined to our hospital either," she said.

"We discovered that there was some sewage leaking in that building, gosh I think it was a couple of years ago now, and there was certainly some publicity around that at the time."

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However, CMDHB subsequently issued a media statement that it was incorrect to say there was "sewage leaking down walls" at Middlemore.

"The occasional plumbing leak is not uncommon in any building, particularly a hospital where we have a high-density requirement for ensuite facilities," it said.

"Some of these leaks are the result of materials being put down our waste system that shouldn't be, leading to blockage."

In 2018, the Government announced an $80 million funding boost for CMDHB so the health board could fix its deteriorating buildings.

The DHB this week said remediation work on buildings with significant weather tightness issues was ongoing.

"Work is ongoing and will take a number of years to complete as it is being carried out while the hospital remains operational," CMDHB's spokeswoman said.

"Sewer stacks that are found to be in or below average condition will be replaced as part of the remediation projects.

"The next remediation projects will follow similar methodologies to ensure all risks are effectively addressed."

External work on the Scott Building was due for completion in February 2022.

The DHB hoped to start three additional remediation projects - Kidz First, Macindoe and Manukau Elective Surgical Centre - in mid-2021.