Act leader David Seymour lobbied for the changes after a briefing made him realise how wide-ranging the new powers could be.
"Immigration officials without a warrant who were searching a business connected to a residence - that might be a dairy or a family-owned restaurant in my electorate - could then enter the residential part of the building where they would be entitled to ask questions with the expectation of having them answered or search for documents without a warrant."
He negotiated changes with Mr Woodhouse, now included in the bill before its final and third reading, including requiring a report from the Ministry of Business, Innovation and Employment on the use of entry and search powers. The report will be delivered to the Immigration Minister not later than three years after the changes, who would then present it to Parliament, opening its findings to debate.
The department would also be required to outline how many times search and entry powers were used, and how many times these significantly contributed to a prosecution.
Mr Seymour said he was not entirely comfortable with the powers being given to immigration officials, but the "facts of life" according to Act's confidence and supply agreement meant he would vote for the bill.
"When you are one of 60, in effect, you just have to use the power you've got responsibly and improve things as much as you can without hijacking the whole legislative process."
Labour and the Greens have said the motivations for the bill are good but some of the "coercive powers" are open to abuse. They say New Zealand needs to create an environment which enables workers to report abuse against employers who are often sponsoring their visas, and this requires visa protection for temporary workers that is missing from the legislation. More funding is needed for labour inspectors, who are best placed to monitor abuses, they say.
More muscle
• New powers to be given to immigration officers which will allow them to search an employer's home without a warrant to look for documents or compel anyone inside to answer questions.
• New amendments to the legislation seek to ensure better monitoring of these powers by requiring Immigration NZ to report how many times they are used and result in prosecution.