RNZ reports a report led by the Commissioner has found major gaps allowing a systemic pattern of human rights abuses.
Those included unreasonable pay deductions, denial of personal and cultural freedoms, poor access to healthcare, and grossly inadequate housing.
Equal Employment Opportunities Commissioner Saunoamaali'i Karanina Sumeo told Morning Report the treatment of workers was distressing to witness.
She described freezing and damp accommodation in Blenheim, with workers not allowed heaters.
"We should not be taking advantage of [workers] and prospering from that through ... what can be seen as modern day slavery."
She said there was humiliating and racist treatment of Pacific workers, with some employers ignorant that they could be breaching staff human rights.
"What I saw was really really shocking.
"The unhealthy conditions, the health and safety issues."
She said some were denied leisure activities and others had their passports taken from them "for safekeeping".
"Those sorts of undertones around intimidation and racism are definitely there.
"And treating people like children who don't know better, that's insulting."
Some workers had said they were physically scared of their employer, she said, and issues had been passed to police to investigate.
Unions had tried to advocate for workers, Sumeo said, but some staff were discouraged from joining and told they would not be allowed back for the next season.
The Commissioner made 13 recommendations to the government, the first being an urgent review of the RSE scheme before the 2023 season, in which 3000 additional RSE workers could be coming into the country.
Others included removing the tie-in of RSE worker visas to a single employer, requiring employers to use standard form offers of employment and contracts containing terms which complied with New Zealand law, improving enforcement of accommodation standards, requiring rents be reasonable in relation to wages earned and ensuring workers are able to use employment protections and redress mechanisms available to all New Zealanders.
Union representatives said they had been barred from visiting staff outside work hours.
Amalgamated Workers Union Wellington regional secretary Robert Popata said a major problem was much of the treatment was allowed on under the RSE scheme.
"What we've said to the minister and to the ministry is, actually, the system needs a complete overhaul. It's no longer fit for purpose."
Popata said the Immigration Minister had asked for employers, unions and government to get together and fix the scheme.
The government said the wellbeing of RSE workers was a priority.
Equal Employment Opportunities Commissioner Saunoamaali'i Karanina Sumeo. Photo: Supplied