While attention has focused on cutbacks to the politically charged 457 visa – which Labor claimed on Wednesday were "already unravelling" – planned changes to the employer-sponsored skilled migration program may have more serious consequences.

That program, chiefly the Employer Nomination Scheme or subclass 186 visa, allows skilled workers to gain permanent residency and settle in Australia. It is open to 36,000 places each year.

But a change slated for March 2018 will see the list of occupations eligible for the program slashed to fewer than 200, excluding such professions as university lecturers, counsellors and management consultants.

"That's actually going to be a really big change. That is the major change out of everything I've seen," said Henry Sherrell, researcher at the Australian National University's Crawford School of Public Policy.

"It changes the way people can recruit, it changes retention, it changes the labour market norms of immigration."

It means people who want a path to permanent residency through their work would be eligible only if their occupation is on the truncated medium and long-term strategic skills list.

The Immigration Department says the jobs on the list "have been assessed as being of high value to the Australian economy and aligning to the government's longer-term training and workforce strategies".

Occupations on the list include barrister, bricklayer, electrical engineer, landscape architect, diesel motor mechanic and locksmith.

Chris Wright, senior lecturer at Sydney University, said it was "still a pretty big list" and could expand in response to future needs of the labour market.

But Mr Sherrell said it would decimate the two-step migration process, replacing it with "the equivalent of guest workers" who had no way to become residents.

Angela Chan, past president of the Migration Institute of Australia, said the medium and long-term strategic skills list was "highly restrictive" and the changes would particularly affect international students who had found employment sponsorship.

"There are lots of occupations on it, but lots of caveats on it too," she said. "The whole thing just seems like a whole lot of bad ideas put together."

Immigration Minister Peter Dutton's office did not respond to questions on the subject by deadline.

Meanwhile, Opposition Leader Bill Shorten portrayed the government's overhaul of the temporary migration system as a "cosmetic job", arguing the decision to trim the list of occupations eligible for a two-year work visa was "not a crackdown – it's a con job".

The opposition released analysis showing just 8.6 per cent of foreign workers currently on a 457 visa were working in jobs that would be excluded under the new system.

Of the 216 jobs being slashed from the eligible occupations list, 18 haven't been used in the past decade. Those jobs include turf growers, deer farmers, homeopaths and detectives.

Another 46 occupations haven't been granted a visa in the past year, including antique dealers, futures traders, park rangers, blacksmiths, gunsmiths, funeral directors and golfers.

But cooks, cafe and restaurant managers, chefs, marketing specialists and programmers – professions for which 457 visas are most commonly used to bring in foreign workers – remain on the list, though they will be subject to the new rules requiring police background checks, two years of work experience and labour market testing.

Mr Shorten said the analysis of the publicly available data, current to December 31, showed "he [Mr Turnbull] is tinkering at the edges for a headline so he can keep his job for another month".

"He's scrapped one visa and created two new ones - not even one in 10 visa holders would be affected," he said.

"Under Malcolm Turnbull, we'll still be bringing in cooks, builders, bakers and hairdressers from overseas to do jobs that Australians should be doing."

Mr Dutton hit back, arguing Labor had granted 21,000 visas over its six years of governance in the job categories he had now scrapped from the list.

Labor had "perverted" the 457 program and the Coalition's changes "will ensure it is cleaned up", he said.