The head of the Employers and Manufacturers Association has slammed New Zealand First's idea of a major reduction in immigration.
The party wants to cut the number of people coming into the country, with the policy likely to be on the table in coalition negotiations this week.
The association's chief executive, Kim Campbell, said reducing immigration would bring the economy to a "shuddering halt fairly quickly".
He said New Zealand First's policy of reducing the number of migrants to 10,000 a year was extreme.
"The fact that immigration could use some recalibration, I don't think anybody disagrees with that, but just these arbitrary numbers are hard."
Mr Campbell said the developed world's population was aging and it would not be long before countries would be competing for people and New Zealand could not be left behind.
"Many of the people coming in are young and energetic and hopefully they will raise our birth rate so the country actually has a possibility to continue to prosper."
And Mr Campbell laughed off Mr Peters' suggestion that the Ports of Auckland be moved to Northland.
He said in the fullness of time the port could be moved but it would take a lot of money.
"Let's pick a number, say $5-6 billion."
Mr Campbell cited transport and roading issues as two of the big problems facing Auckland.