Changes to immigration policy will make it tougher for migrant workers thinking of coming to New Zealand, but will ease requirements for some who have lost their jobs and are already here.

Migrant workers who lose their jobs during the probationary 90-day period will not only get a further three months' visitors permit, but their children will also be allowed to continue schooling as domestic students.

However, those coming to NZ on a seasonal employment scheme can no longer support applications by their partner or dependent children to come here too.

As well, visas issued under the essential skills work policy will be limited to one year for lower-skilled workers.

The amendments will be effective from July 27, says Immigration NZ.

Richard Howard, chairman of the Association for Migration and Investment, said allowing applicants placed in this situation to have their children continue to attend school as domestic students, albeit for a limited time, "is the first policy sign we have seen of this Government considering the actual and practical impact on migrants and their families when faced with a job loss situation".

"The policy allows the children to at least maintain their schooling while their parents decide on the family's future."

The changes are a surprise even for migrant advocacy groups such as Migrante Aotearoa, which is running a campaign for Immigration NZ to grant a three-month extension to the permits of temporary migrant workers made redundant in the recession.

"We knew it was on the agenda for the proposed immigration bill, but I am totally surprised that it has already been adopted into policy," said the group's Dennis Maga.

"At last there is some common sense, but the policy changes have to go further to include those outside the probationary period - because the real problem is with the workers facing redundancies after having been here for years and years."

Many migrant workers made redundant while on a work-to-residence visa, and those who were victims of the Labour Department's removing 44 occupations from its skills-shortage list would not be eligible to apply for the three-month extension, Mr Maga said.

With the changes, Immigration NZ will be adding 19 occupations to the skilled list, including advertising manager, retirement village manager, radiation oncologist and first aid trainer.

The relaxing of rules comes at a time of soaring unemployment with the number on the unemployment benefit topping 50,000 - almost three times the number a year ago.

Engineering, Printing and Manufacturing Union national secretary Andrew Little supported the changes, saying the three-month permit was "minimal mitigation" for a practice that should not be there in the first place.

"I would argue that a worker in this situation should not be dismissed without good and sufficient reason. Amending immigration policy to accommodate such an unjust occurrence is minimal mitigation of the injustice, at least for migrant workers," said Mr Little, who is also president of the Labour Party.

"For a migrant worker who has come here on the offer of a job, and who has uprooted his or her family to take up the offer to then be subject to an arbitrary decision to dismiss is unconscionable and highlights the shortcoming of the dismissal law."

The Department of Labour, which oversees immigration, was unavailable for comment.

* Immigration policy amendments (effective July 27)

Temporary migrant workers dismissed within a 90-day trial period may be granted a further three months' temporary permit. Their partners and children may also be included in the application; dependent children qualify as domestic students.

Migrant workers on supplementary seasonal employment will no longer be eligible to support their partner and children for permits under visitor, student or work policies.

Visas issued under the essential skills work policy will be limited to one year for lower skilled workers.

19 occupations have been added to the skilled occupation list, including software tester, public relations manager, equipment hire manager, canvas goods fabricator and phlebotomist.