On average, New Zealand has had one of the fastest-growing populations in the developed world.
But infrastructure and housing aren't keeping up, according to the preliminary findings of the Productivity Commission's immigration inquiry.
"Immigrants make an important contribution to New Zealand society," Productivity Commission chair Ganesh Nana said in a statement. "Immigrants bring diversity and much-needed skills to workplaces across the country and have supported the delivery of important public services either directly or through their net contribution to the Government's finances."
However Dr Nana said New Zealand isn't accommodating more people well - and it's struggled to do so for a long time.
"Infrastructure and housing supply have not kept up with population growth, creating pressures that affect the wellbeing of both migrants and New Zealanders.
"To ensure immigration contributes to the productivity and wellbeing of New Zealanders, governments need to build the assets and infrastructure needed to support a growing population, in preparation for the number of new residents, ahead of time."
Several changes are being recommended to ensure future immigration settings have better outcomes, the commission said.
"The law should be changed to require governments to explicitly consider how well New Zealand can support and settle more people," the commission said in its preliminary findings.
It also wants the Government to publicly say what its priorities and objectives for immigration are "and the steps it will take to ensure that public investment matches need".
"A country that treats its guests well is more likely to attract migrants, retain their capabilities and enjoy their long-term contributions."
In the past, visa conditions have tied migrants to specific employers. The commission wants those conditions removed.
"These conditions make migrants more vulnerable to exploitation and limit the ability of migrants to find jobs that best meet their skills and experience," Dr Nana said.
Looking at the Treaty of Waitangi, Dr Nana said it needs to be recognised when considering future immigration policies.
The treaty is barely mentioned in current immigration policy documents, he said.
Dr Nana said the Crown needed to protect Māori interests.
"With regards to immigration policy, this has implications for both Māori businesses and Māori workers.
"Māori workers may also be disproportionately affected by immigration’s effects on wages, employment and conditions at an industry or local level.
"Although the commission's research finds that immigration has very minor effects on the labour market as a whole, effects on the young and beneficiaries remain a concern."