LONDON — Britain's decision to leave the European Union is putting at risk billions of dollars the country receives from foreign students, who increasingly are choosing to study in the United States and other English-speaking nations.

The United Kingdom is the second most popular destination after the U.S. for international students, who contributed more than $33 billion to the U.K.’s economy in 2014-15.

Now, many of those students are going to Canada and Australia, in addition to the U.S. as Britain's formal 2019 exit from the EU nears.

A 2016 survey by the student recruitment consulting firm Hobsons found that 30% of international students said they were unlikely to come to the U.K. to study following the referendum earlier that year to leave the EU. Another 6% said they would definitely not choose Britain to study as a result of the Brexit vote.

Government figures also showed the number of Indian students at British universities fell 10% in the past year because of concerns about immigration.

The loss is costly. According to Oxford Economics, spending by international students in 2014-15 supported 206,600 jobs in U.K. university towns and cities. International students pay tuition ranging from $12,000 to $43,000 a year, while British and EU students pay up to $11,380 a year.

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Yinbo Yu, 25, an economics student from China who represents international students in the National Union of Students, said some of his friends who did their undergraduate degrees in the U.K. were moving to Australia, Canada and the United States for their masters or further study.

In Australia, nearly 50,000 Chinese students began courses in 2016, up 23% from 2015. Gary Fan, a student at the University of Sydney's business school, told the Financial Review website that one of the draws for him was a temporary graduate visa that allows students to work in Australia for up to four years after they graduate.

By contrast, Yu said, the U.K. government has scrapped a post-study work visa program and is now charging them to use the National Health Service.

Moreover, Prime Minister Theresa May’s government has classified foreign students as immigrants as part of a drive to lower net migration to less than 100,000 a year. Unlimited immigration from EU countries was a major reason the Brexit referendum passed.

“The government really has to look into these issues and find ways to protect our international students,” Yu said.

The U.K. government says its restrictions on foreign students stems from the fact that many remained in the country illegally after completing their studies.

“The British government wanted for some really good reasons to tighten up some things and they’ve sort of overdone it,” said Keith Burnett, vice-chancellor of the University of Sheffield. He is co-founder of #WeAreInternational, a campaign that aims to show foreign students that they are still welcome here.

The University of Sheffield attracts nearly 7,000 international students from more than 140 different countries. Another university in the city, Sheffield Hallam, has more than 3,000 international students, 42% of them from China, 10% from Nigeria, 9% from Malaysia and 8% from India.

Aware of the potential loss of revenue, the government has commissioned a study to be completed by next September on the impact of international students. "The Government strongly wishes to continue to attract international students to study in the UK," Home Secretary Amber Rudd said of the assessment.

“It’s very important we keep up the message that there are open, welcoming communities across the United Kingdom," Burnett said.