Housing Minister Megan Woods said the increased numbers were down to Kāinga Ora doing more jobs than under the previous government, like consenting.
"What the staffing numbers tell is a story of a Government that since 2017 has recognised there is a housing crisis and that it has an active role to play in fixing that crisis."
She said that under National, the organisations that became Kāinga Ora were "shedding staff", which told a story of "a Government that washed its hands of any responsibility to deal with the fact that we simply did not have enough houses in New Zealand".
"We simply did not have enough houses in New Zealand. Housing NZ, the predecessor to Kāinga Ora, was selling off houses and it was shedding staff."
Woods said the Government now had about 3000 homes under construction, up from about 350 homes under construction in 2016, which she said showed the additional staff were having an effect on the housing programme.
"They are development managers, they are project managers, they are quality assessors, they are architects."
But Willis said that despite the additional staff, Kāinga Ora was falling below expectations for house building.
In 2019-20, the agency's statement of performance expectations asked that it build 1500 new state houses. Instead, it built 1229.
Kāinga Ora says this period included the first Covid-19 lockdown, when it was prevented from entering building sites, which is why it failed to meet that target.
"The simple fact is that Kāinga Ora has failed its targets," Willis said.
"It completely failed its KiwiBuild target. It's fallen behind on getting state houses up to healthy home standards. It's been buying up homes throughout the country."
Kāinga Ora has also added a consenting authority, employing 48 fulltime equivalent staff which allows it to quickly consent its own public housing developments, rather than going through a council.
This has caused tension with some councils who in the past have complained that Kāinga Ora has poached their staff, making it more difficult for councils to do their consenting work.
A spokesperson for Auckland Council acknowledged that it had "lost some resources to Kāinga Ora in the past", but was taking "a partnership approach to helping the agency deliver on the Government's agenda to address the housing situation in New Zealand".
Willis said this hiring-go-round demonstrated the broken nature of New Zealand's consenting system.
"The resource consent process holds up houses from being built. The Government should be focused on solving that for all housebuilders, not just the government housebuilder."