The Public Service Commission says Immigration New Zealand should have done more to minimise the risk of abuse to the work visa scheme.
The Accredited Employer Work Visa scheme, which has been in place since July 2022, has faced criticism for not protecting workers adequately.
The scheme was brought in after Covid-19 border closures led to worker shortage.
In order to reduce visa processing times the number of checks required by immigration officers were reduced.
There have been multiple reports of migrants being brought over by the scheme living in overcrowded housing and left jobless and immigration advocates have been calling for the scheme to be paused.
The Commission has released the findings of an independent review of the scheme, led by Jenn Bestwick, which looked at whether Immigration New Zealand had mitigated the risk of migration exploitation appropriately.
The review found while INZ's decision to reduce the checks was reasonable under the circumstances, it did not adequately assess the risk and impact of the changes to speed up processing times would have on visa abuse.
When INZ staff did raise concerns about the risks, that INZ leadership "failed to pay adequate attention", the review found.
The report said multiple staff members raised concerns with senior managers that migrants had paid large amounts of money to secure a job and visa, and were giving scripted responses to officials to conceal this fact.
Some workers were not getting paid at all, and ineligible employers were being granted accreditation by officials, they said.
Frontline INZ staff felt that responses from their bosses were dismissive and that issues raised were "swept under the carpet".
Deputy Public Service Commissioner Heather Baggott said changes to the scheme did not work as intended and INZ should have done more to minimise risk of abuse of the work visa system.
"Immigration New Zealand implemented, very quickly, a new model to accelerate immigration at a time the country desperately needed skilled workers."
"While it was unscrupulous employers who exploited migrants coming into the country, Immigration New Zealand could have, and should have, done more to minimise the risk of that happening."
She said Ministry for Business, Innovation and Employment chief executive Carolyn Tremain had since made or was undertaking the necessary changes to the scheme to ensure it better protected migrant workers coming into the country,
"I expect the chief executive will continue to make improvements in line with the recommendations identified in the report. And the chief executive has assured me this will happen."
As at 14 August 2023, Immigration New Zealand had approved 80,576 Accredited Employer Work Visa applications, and there were 27,892 accredited employers.
By 16 February 2024, MBIE had received 2107 complaints against accredited employers.
One hundred and seventy-four employers are currently being investigated, 145 employers have had accreditation revoked, 53 have had accreditation suspended, and 48 employers are under assessment to have their accreditation revoked.
Last year then-Immigration Minister Andrew Little said the scheme would be reviewed after he received an anonymous letter from an internal whistleblower.
"The particular allegations were that some checks on employers were not being made, and some checks as part of the job check process were not being made," Little said.