According to the notification, the new visa programme will cut more than 200 eligible jobs for skilled migrants - from 651 to 435, visa fees are set to increase, and the visas will be restricted to filling "critical skills shortages".
"We will no longer let 457 visas be passports to jobs that could and should go to Australians".
In a "major announcement" on Facebook, Malcolm Turnbull said: "We're putting jobs first; we're putting Australians first".
"Who really believes that given an option between an Australian resident and a visa holder with the same experience/qualifications we would choose the visa holder?"
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The 457 visa is created to give businesses the option of employing foreign workers in the event that suitable candidates can not be found in Australia.
For people now on the 457 visa, there will be no changes to their situation and they will be able to continue to work under the current conditions of their 457 visa.
As the economy has tightened - particularly in Western Australia where the mining industry has contracted considerably - the programme has come under fire, especially from unions which claim it is prioritising foreign workers for jobs over Australians.
The minister for immigration and border protection Peter Dutton said the changes were "an attempt to clean up Labor's mess".
As well as putting some job seekers offside, a parliamentary enquiry previous year found the visa system left foreign workers open to exploitation, and that many were being underpaid or otherwise taken advantage of as a result.
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Mr Turnbull was out defending the new two-year and four-year visas on Wednesday, warning the labour market testing requirements would be rigorously policed.
The changes were made to ensure that the program met the skills needed in Australia and increase the quality and economic distribution of skilled migrants.
Responding to a query, External Affairs Ministry spokesperson Gopal Baglay said that the government was examining consequences of the new policy in consultation with all stakeholders.
What is a 457 visa?
He says there are still jobs Australians don't want to do, "whether it is packing offal in an abattoir or boning out skulls".
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Mr Turnbull was tight-lipped on the arrangement and said it would be detailed in the budget. Just under 2,000 temporary visas were granted to Irish citizens between 2015 and 2016, excluding secondary applications.