Winston Peters has accused the Government of pulling an immigration "con" with its latest shake-up of policies.
The plans include a remuneration threshold for skilled migrants, new visa time limits, stand-down periods and tighter regulations for partners.
The New Zealand First Leader says the Government's only responding to the polls in a callous attempt to hold on to power.
"We are skilled-labour short because we haven't trained people despite the Christchurch earthquake and all the warnings we had."
Immigrants earning less than $49,000 a year will no longer be considered highly skilled under the new rules.
Mr Peters says Labour's record isn't much better.
"The Labour Party supported mass immigration all through the 1990s and the 2000s, and now they say all of a sudden they're concerned. Well, it's a bit late when you were a part of the problem in the first place."
An immigration adviser has also labelled one of the changes as unreasonable.
Southern migrants are allowed an easier route to residency than those who settled in the same jobs in the North Island.
David Cooper has worked in the sector for 25 years, and says the amendment goes too far.
"Those other migrants in the North Island have made just as much of a contribution to New Zealand as those ones down south."
Mr Cooper says the rest of the changes are understandable.
"At the end of the day, it's got to be what's in the best interests of our country. Of course we want migrants to have a better life, but we've got to be careful about who we bring in."