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As migrant numbers swell, analysts say the issue at Calais could become a flashpoint that reignites debate in a country where concern over immigration is particularly widespread.

“Concerns about the security of the border and immigration’s association with asylum are often associated with more negative attitudes,” said Scott Blinder, director of Oxford University’s Migration Observatory.

“Since it has been on the agenda for polls and surveys, there [have] been pretty similar, high levels of opposition in terms of British people saying there is too much immigration and there should be less,” Mr. Blinder added.

According to a 2013 poll conducted by the Migration Observatory, more than 50 percent of Britons thought there was too much immigration and more than 60 percent saw migrants as a problem and not an opportunity, compared to fewer than 30 percent of Swedes who felt the same way.

Mr. Blinder said negative attitudes could stem from politicians’ framing of immigration as a “problem to be solved,” as well as the effects of the recession and Britain’s decision to open its labor market to new EU member states the Czech Republic, Estonia, Hungary, Latvia, Poland, Lithuania, Slovakia and Slovenia in 2004 before it had to do so.

“This is why Britain is exceptional to the rest of Europe. People consistently refer back to this as a huge mistake,” Mr. Blinder said. “Eastern Europeans settled in a broader swathe of the country, not just in London, so that could have brought concerns to broader sections of the country.”

A nation of more than 64 million people, Britain has an illegal immigrant population of more than 500,000, according to a 2005 study. With a per capita gross domestic product of about $37,300, Britain enjoys a strong economy and has communities from nearly every quarter of the world, making it an attractive destination for illegal immigration.

Overall, the number of people entering the U.K. has been greater than the number emigrating from the country since 1994, and Balanced Migration, a cross-political party group, projects Britain’s population will reach 70 million by 2027 and that two-thirds of that growth will be a result of immigration.

The organization says this will place new pressures on schools, the state-run National Health Service and the police, and it is calling on the government to balance the numbers.

The British government did vow to reduce net migration — the difference between the number of people entering and leaving the country during the year — to the tens of thousands by the national election, but with current net migration levels at 212,000, this seems impossible.

Prime Minister David Cameron’s Conservative government also has shifted focus from border security and pre-entry checks to in-country control with the 2014 Immigration Act. Immigrants now must pay a new health care levy, and landlords are responsible for checking their tenants’ immigration status.

Ruth Grove-White, policy director at Migrants’ Rights Network, said looking at immigration as a numbers-based issue is “missing the point.”

“The achievements of migrants are embedded in the achievements of the nation — the role migrants play is integral to what it means to be British,” said Ms. Grove-White.

“Immigration has made a huge contribution to the economic, cultural and social fabric of the U.K. Look at the contribution in the NHS, where up to 40 percent of nurses are migrants,” she said.