The UK's post-Brexit immigration system will deny visas to low-skilled workers, the government has said.
A new points-based system - to be introduced from January 2021 - is intended to end dependence on "cheap labour from Europe".
Ministers claim they will also make it easier for higher-skilled workers to get UK visas.
But critics say the proposals could be an "absolute disaster" for the social care sector, and there are "serious concerns" about the impact on farming.
The Home Office estimates 70% of EU workers currently in the UK would not meet the requirements if applying under the new system.
The salary threshold for skilled migrants will be lowered from £30,000 to £25,600, but those coming to the UK must already have a job offer and speak English.
EU and non-EU nationals will be treated equally with priority given to those with "the greatest talents", such as engineers and scientists.
If an applicant earns less than the threshold - but no less than £20,480 - they may still be able to come if they are skilled in an area with a shortage of labour.
Home Secretary Priti Patel told Sky News' Kay Burley @ Breakfast show: "This is a very significant moment in the UK's immmigration policy.
"This is the first time in decades the government has been able to take back control, run its own immigration system after we've left the EU, end free movement, end low-skilled migration to our country; which means that we will get migration numbers down.
"That is central to this policy of a points-based system."
However, Ms Patel did not reveal by how much immigration would fall under the new system, with the Conservatives having abandoned their previous long-held pledge to reduce net migration to below 100,000 per year.
"We're not getting into the sphere of targets at all," she said.
Ms Patel added: "Success for us is actually having a vibrant economy.
"An economy that is supported by high skills from individuals that come to our country on the points-based system that can contribute to our economy."
The home secretary stressed a fast-track visa system for NHS workers would protect hospitals from staff shortages under the new immigration plans.
But the Confederation of British Industry (CBI) has warned the care, construction, hospitality, food and drink sectors could be most affected by the changes.
Christina McAnea from Unison, which represents care workers, said: "These plans spell absolute disaster for the care sector. Care doesn't even get a mention in the home secretary's plans.
"Companies and councils can't recruit enough staff from the UK so have to rely on care workers from elsewhere. But even with these migrant employees, there's still way too few care workers to meet demand."
The Royal College of Nursing also said the proposals would "close the door" on lower-paid healthcare workers, while the UK Homecare Association warned it could mean more people "waiting unnecessarily in hospital or going without care".
National Farmers' Union president Minette Batters argues the proposals could "severely impact the farming sector".
The Food and Drink Federation (FDF) praised the reduction of the skilled worker salary threshold, but was cautious about the impact on less skilled workers in food production.
Mark Harrison, a spokesperson for the FDF, said: "We have concerns about access to those potential employees who won't qualify through these 'skilled' routes such as bakery assistants, meat processors, and workers essential to the production of huge array of basic foodstuffs such as cheese, pasta, and sausages."
Ms Patel later faced questions over whether her own parents, who moved to Britain from Uganda in the 1960s, would have been barred entry to the UK under the new immigration system.
Her parents came to the UK before former Ugandan president Idi Amin ordered the expulsion of the country's Asian minority.
Ms Patel told LBC Radio: "This isn't about my background or my parents.
"This is a very different system to what has gone on in the past and don't forget this is a points-based system based on the labour market."
She added: "The policies are changing. This is the point. We are changing our immigration policy to one that's fit for purpose for our economy, based on skills.
"This is not about refugees and asylum and people being persecuted around the world. We must differentiate between the two."
Labour's shadow home secretary Diane Abbott told Kay Burley @ Breakfast: "Talking about immigrants as if they're a problem is not the sort of leadership that government ought to offer.
"The Labour Party celebrates the contribution of immigrants.
"We want a fair system, we won't play the Tories' dog-whistle politics."
Scottish First Minister Nicola Sturgeon repeated her call for Scotland to get its own immigration powers after the UK government unveiled details of the new scheme.
She posted on Twitter: "Tory immigration policy is offensive in principle - it labels vital workers, making a big contribution as 'low skilled' & slams the door in their faces.
"And it is disastrous in practice - it will badly damage our economy.
"We must get powers to create policy for our needs & values."
Liberal Democrat home affairs spokeswoman Christine Jardine said the proposals were based on "xenophobia" and not the "social and economic needs of our country".