ACT has launched its immigration policy ahead of this year's election - with surcharges and tougher limits for serious offenders. 

It includes a $6 a day infrastructure surcharge on temporary work visas, which is expected to pocket $80 million a year.

The party also wants stronger English language requirements, and would also establish a dedicated unit around enforcement for people over-staying their visas.

Leader David Seymour says New Zealand was built on immigration, but it's important to keep the right balance.

"What those waves of settlement have done is two things. One is that they built a Kiwi character that's the envy of the world...whether it's our troops out there doing peacekeeping, our sportspeople, our businesspeople - Kiwis have a reputation that we can fix anything, we do what we say we're going to do, we're compassionate and thoughtful people."

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