Oli Khan, a spokesman for the Bangladesh Caterers Associations, says that Britain’s beloved curry industry is hurting as a result of the country’s visa restrictions. (Karla Adam/The Washington Post)

When Shannon Harmon moved to the United Kingdom from Chicago, she did not plan to put down roots. But after nearly eight years, she has a master’s degree from a prestigious British university, works as a digital producer at a science-news organization and has built strong ties in her local community.

She also has a massive, five-figure problem: She earns less than 35,000 pounds, or about $50,000, which means that under new visa restrictions introduced this spring she could be deported after her visa expires in January 2018.

The new rules require immigrants on skilled-worker visas from non-European countries, including Americans such as Harmon, to earn at least 35,000 pounds if they want to settle here. Critics of Britain’s immigration policies say that the country is, effectively, rolling up the welcome mat for non-Europeans who do not make enough.

[Immigration backlash at the heart of British push to leave the E.U.]

“For me, getting a raise from 25K to 35K is pretty unimaginable,” says Harmon, a 33-year-old with bright red hair who wants to stay in the United Kingdom but earns only 25,000 pounds. She is a driving force behind Stop35k, a grass-roots campaign against new visa restrictions that triggered a debate in Parliament.

The changes to Tier 2 visas — the equivalent of the H1B in the United States, given to skilled workers from outside the European Union — come amid an increasingly intense debate over Britain’s membership in the E.U. Britons will head to the polls this month for an in-or-out referendum that has pushed the issue of immigration onto center stage.

In recent days, the momentum has swung towards the campaign to leave the E.U., also known as "Brexit," with its supporters arguing that Britain is overflowing and that something needs to be done to limit numbers.

“The system has spun out of control. We cannot control the numbers,” lawmaker Boris Johnson has said.

As a member of the E.U., Britain has to abide by freedom-of-movement rules, meaning it cannot bar entry to citizens from the 28-nation bloc. Curbing the number of non-European immigrants is one of the few alternatives the government has.

The British government is “focusing on non-Europeans because this is the only group they can really control under the current conditions as a member of the E.U.,” said Franck Düvell, a professor at the University of Oxford’s Center on Migration, Policy and Society.

[As polls tighten, Cameron pleads with unhappy voters to back away from ‘Brexit’]

British Home Secretary Theresa May, whose department is responsible for implementing the changes to settlement rules, has said that they will encourage employers to train a home-grown workforce to “ensure that our migration system does not perpetuate reliance on migrant labor.”

"In the past it has been too easy for some businesses to bring in workers from overseas rather than to take the long-term decision to train our workforce here at home,” the Home Office said in a statement. "We need to do more to change that, which means reducing the demand for migrant labour.”

May has said that the new restrictions will reduce the number of non-E.U. migrants being granted residency by up to 40,000 a year.

Britain remains a hugely attractive draw for migrants who are not easily deterred by rocketing house prices or a national obsession with talking about the weather.

The country boasts a number of excellent universities and has the advantage of being an English-speaking country in Europe. Britain’s buoyant economy has prompted Prime Minister David Cameron to call it “the jobs factory of Europe.”

[A British vote to leave the E.U. could shatter the United Kingdom]

But the United Kingdom’s status as a country of mass migration has put pressure on hospitals, schools and transportation in some areas. It is also a source of deep embarrassment for Cameron, who pledged to reduce net migration — the number of people arriving minus the number of people leaving — to less than 100,000.

New figures recently published showed net migration in 2015 at more than three times that figure. The Sun tabloid responded by printing on its front page an image of Cameron with his eyes closed and fingers in his ears, seemingly trying to ignore the statistics while muttering “la la la.”

The new visa restrictions for non-E.U. workers include increasing the salary threshold for those living in the United Kingdom for less than 10 years who want to settle here. Previously, after five years, migrants on a Tier 2 visa could apply for permanent residency if they earned at least 20,800 pounds; as of April, that threshold has jumped to 35,000 pounds. These new rules do not apply to those with PhD-level jobs, workers on the “Shortage Occupation List” and nurses, who were made temporarily exempt after an outcry that not doing so could put patients at risk.

The changes have sparked a debate about whether income is the right measure for deciding who can stay and who must go and whether salary thresholds should be tweaked across industries and regions.

“Whereas there might be places in the middle of London where 35,000 is regarded as some sort of miserly salary, I can tell honorable members that it is regarded as a very good salary indeed in my constituency,” Tommy Sheppard, a lawmaker from Edinburgh, Scotland, told Parliament during a debate on the issue.

Campaigners say that Britain’s tough immigration policies unfairly target those in lower-paying jobs, including those in health, technology, charity, arts and creative sectors.

Britain’s curry industry — purveying a favorite dish — has also felt the heat of the country’s immigration policies. Under new entry rules that were recently implemented, restaurants that want to hire skilled chefs from outside the E.U. have to pay a minimum salary of 29,750 pounds, along with food and accommodation, to qualify for a Tier 2 visa.

“Nobody can afford that for a chef,” said Oli Khan, a spokesman for the Bangladesh Caterers Association, a trade body. An owner of three curry houses, Khan says that a top chef makes around 25,000 pounds and that the industry is, reluctantly, moving away from hiring chefs from India and Bangladesh to hiring those from Eastern Europe, whom he says do not have the same “passion” for cooking curries.

Some proponents of Brexit argue that if Britain votes to leave the bloc on June 23, it would create a fairer system for skilled workers outside the E.U.

“By voting to leave, we can take back control of our immigration policies, save our curry houses and join the rest of the world,” Priti Patel, Britain’s employment minister, recently told the Evening Standard.

Kymberly Blackstock, a 35-year-old from Seattle, is one of those caught up by the new visa restrictions. A mother of two young children, Blackstock earns 21,800 pounds a year working for a charity in Scotland. Her husband, a dependent on her visa, works night shifts as a careworker for the elderly.

She does not think it is fair that her salary may determine whether her family can settle in the United Kingdom after her visa expires.

“We make a much bigger social contribution to the society than somebody sitting at some management office at a bank,” she said.

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Today’s coverage from Post correspondents around the world