Mr Key told Radio New Zealand trying to find out how many migrants might take up the scheme was not a "perfect science".
He admitted people could technically use the scheme as a "back-door way" to live in Auckland, but a number of factors would have to line up in order to do so.
"Your argument could be they could use this as a back-door way of getting into Auckland. Yes, that's technically possible but they would have to end up having a job and all those other things and if they do they may well replace some of the ones who would have come in under the skilled migrants [scheme]," he said.
Local Government New Zealand's President Lawrence Yule, who is also the Mayor of Hastings, said there will be some work available for new migrants.
"A lot of people who move into the regions that are migrants actually end up creating their own businesses and their own opportunities," Mr Yule said.
"What you tend to find in regions is outsiders come in, and they look at things in a different way and they find opportunities that often the locals can't quite see."
Those who set up businesses outside Auckland will be given 40 extra points, doubled from the current 20.
Mr Yule said although the migrants may not all ultimately stay, many of those who start something of their own will.
Sociologist Paul Spoonley said regions faced the challenge of being more welcoming, to ensure migrants actually stay beyond the new 12 month minimum.
He thinks many migrants are drawn to Auckland, for good reasons.
"Auckland is where our large immigrant communities are based, so if you go to some regions you are going to find very few from your community in that region."
During his speech yesterday, the Prime Minister assured New Zealanders would always be first in line for jobs, and said Auckland, as the country's largest city, would continue to grow.
"We're not making it harder to come to Auckland, we are making it more attractive for people to go around the regions. Now we do have that soft cap that sits at around 45,000 to 50,000 people, but I don't think it will have a dramatic impact."
Mr Key said there was no question some people would see an easier pathway when they looked at what was on offer, but he couldn't say how many.
"We can't tell you exactly up front. It will make it certainly more attractive, I don't know the exact numbers. I do know that there is capacity in the regions, that there is demand in the regions, and we've seen migration flows be very successful there."
New Zealand First Leader Winston Peters views the rule change as an admission from the Government that it has a crisis in Auckland.
"They're doing this as a cut and paste to try and show that they're doing something," he said.
Until now employers could not communicate directly with Work and Income about overseas job applicants.
Immigration Minister Michael Woodhouse said employers have been calling the process cumbersome.
"What we are getting is employers speaking to Work and Income much more proactively. So that they understand what New Zealanders are available to do the jobs, and when it's not it is a much smoother process to gain visas for overseas workers."
Yesterday, the Prime Minister stated the party should be cautiously optimistic about its prospects for the next election.
His deputy and Finance Minister Bill English was centre stage yesterday, with an upbeat message about the economy.
"We have every confidence that New Zealanders will be able to adapt where they need to, to the economic pressures that are changing, but continue to look ahead positively about the investment they can make and the opportunities they can create."
He said New Zealand was on track for sustainable, moderate growth.
He expressed confidence in the party's ability to lead into the future, if it can maintain public support.
"We can make fundamental long term change to the way New Zealand works, and the outlook for every New Zealander."
The Government's full immigration reform includes:
• Skilled workers who take jobs in the regions will have bonus points bumped up from an extra 10 to an extra 30 points.
• Those who set up businesses outside Auckland will be given 40 extra points, doubled from the current 20.
• Employers will be able to contact Work and Income directly to check whether New Zealanders are available to fill a particular vacancy before they lodge a visa application with Immigration New Zealand.
• A pathway to residence will be provided for a limited number of long-term migrants on temporary work visas in the South Island.
Reaction to the new rules
Government hopes of boosting economic and jobs hopes in the provinces by encouraging a greater geographical spread of immigrants have a tentative thumbs-up from parliamentary rival and Napier MP Stuart Nash.
"I thought about it for a while, and I thought, well, let's give it a go," he said last night.
"It is an instrument, there's a whole lot of stuff that can be done, but anything that helps get the regions going has got to be good."At the National Party conference in Auckland yesterday, Prime Minister John Key outlined changes he says will benefit regional New Zealand with skills, labour and capital that migrants can bring to the country.
"Our future is in being open to the rest of the world, in connecting with other countries and making the most of those linkages," he said.
"We welcome migrants who can make a contribution to New Zealand, and we value the benefits and opportunities that free-trade agreements can deliver. If we can get an equal crack at all markets we are up there with the best in the world."
New measures to take effect in November include boosting bonus points for skilled migrants applying for residence with a job offer outside Auckland from 10 to 30 points, doubling Entrepreneur Work Visa points for those planning businesses in the provinces from 20 to 40 points, and streamlining labour market tests to provide employers with more certainty, earlier in the visa application process.
In addition, from mid-2016 a pathway to residence will be provided for a limited number of long-term migrants on temporary work visas in the South Island.
"I'm not going to diss it," Mr Nash said. "But let's see. It's not going to cost the Government anything."
He said the major priority for the regions is restoring regional development funding.
"That's where the real difference will be made," he said.
Dunedin Mayor Dave Cull has welcomed measures to give prospective immigrants to New Zealand greater incentive to go to the provinces.
A series of measures encouraging the spread of immigrants throughout New Zealand was outlined by Prime Minister John Key yesterday at the National Party conference in Auckland.
The changes would increase the number of residency points skilled migrants received for a job offer outside of Auckland, and the length of time they would need to stay in that region.
They would also double the number of points given to an immigrant on an entrepreneur work visa setting up business outside Auckland.
Mr Cull said the announcement was "a step in the right direction ... from a number of points of view".
"Auckland has got enough to deal with without taking all the migrants that come into the country. It just exacerbates some of the problems they're dealing with.
"And there are real challenges in the provinces, not the least of which are demographic.
Populations are ageing and diminishing; they still need younger people to do a lot of the jobs."
