Baby Neve is not the only thing keeping the Arderns awake at night. The Prime Minister and her family appear to have a chronic possum problem at their Wellington home.

A group of the pesky marsupials have taken up residence in the walls and on the roof of Premier House – the official residence of the Prime Minister in the capital.

The Herald on Sunday understands Jacinda Ardern and Clarke Gayford first thought the noise was rats in the kitchen and made attempts to snare the pests in the middle of September.

But a couple of days later the scrabbling noises were back, in the walls and on the roof.

And they were so loud - waking them in the night - that they realised the noise must be possums. The exterminators were called in.

Ardern said it sounded like a cat walking around on the roof and in the walls. The extent of the infestation was not known: "I just know they're there."

"They seem to keep similar hours to us," she added. "I don't hear them so much at night, they seem to be out and about more in the early morning."

While stopping short of pointing the finger at previous tenant and National Prime Minister Sir John Key, she said the possums "may well have been there for a while".

The Department of Internal Affairs (DIA), which manages Premier House on behalf of the Government, said that a pest control company had been working at Premier House for the past three weeks "in relation to a possum issue".

"The work is still ongoing," the DIA said, noting that it has been employing pest control on and off at the house since 2012.

Earlier this week, it was revealed Premier House was receiving a $1 million upgrade.

A spokeswoman from DIA said this would be going towards "routine property upgrade, as part of DIA's ongoing asset management processes, including budget allocation".

Speaking to Newstalk ZB's Mike Hosking this week, Ardern said the upgrade was partly for security reasons but also because parts of the stately home were run down.

"Until recently, when it rained buckets were put upstairs, so a bit of roof work was required."

The upgrade "isn't going to fix the fact we have possums in the roof as well", she said.

Marion Cowden, Chairwoman of the Thorndon Residents' Association – the suburb where Premier House is located – said it's not surprising to hear that the official residence had a pest problem.

"Premier House boarders right onto the bush area in that part of the town so it's not surprising – there is a major program underway to get rid of predators of native birds."

Possums are a major problem in the capital, according to the Wellington Regional Council.

"Because of their feeding habits, possums pose a serious threat to the biodiversity of the Wellington region," the council's website said.

The problem is so apparent that the council is aiming to make Wellington the first "predator free capital city in the world". That means no more possums.