By Aisha Labi

London

Britain's immigration minister said in a speech on Monday that the country must look into capping what he called "unsustainable levels of net migration," much of it driven by international students.

The minister, Damian Green, delivered the speech to the Royal Commonwealth Society following the publication that day of a report by the Home Office, Britain's interior ministry, examining immigration statistics from 2004 and 2009. The report, "The Migrant Journey," found that the largest group of visas granted in 2004 was to students, and that of the 185,600 people who received student visas, more than a fifth remained in the country five years later. With student numbers continuing to rise quickly—in the 12 months to June 2010, more than 320,000 visas for stays of over six months were issued to students and their dependents—Britain must seek ways to bring down migration numbers, the minister said.

"Most people think foreign students come here to attend our top universities and, of course, these are the students we want to attract," but in fact many students enter Britain to study in other sectors of the higher-education system, he said. Mentioning public and private vocational schools, language schools, and other nonuniversity institutions, he added, "The foreign students attending these various establishments may, or frankly may not be, the brightest and the best." The student visa system, he added, needs to do a better job of encouraging "the entry of legitimate students coming to study legitimate courses."

The new figures from the Home Office report highlight the scale of the challenge, and Mr. Green said that placing new limits on immigration "will relieve pressure on public services and stop immigration being such a delicate political issue."

Mr. Green's remarks come at a time when financing constraints mean that British universities are facing a severe shortage of places for students, and the universities minister, David Willetts, has been taking pains to diversify Britain's higher-education landscape by encouraging a greater role for institutions outside the university sector.

Universities UK, which represents university vice chancellors, issued a statement welcoming the immigration minister's differentiation between international students coming to study at universities and those coming to vocational and language schools. "International students provide an important financial contribution to our universities, but their academic contribution is also crucial," the organization said. "They account for over 40 percent of our postgraduate students and are a significant proportion of students in subject areas such as engineering, sciences, and mathematics." The statement warned against any "changes to the system that may hinder the mobility of international students to universities" and said that universities need to be consulted about any policy shifts.

The National Union of Students, the main student union, responded angrily to the minister's speech, saying in a statement that the failure of government agencies to monitor the system, under rules that were recently revised to curtail abuses, and "eradicate bogus colleges that exploit students will not be solved by wielding the blunt instrument of an arbitrary cap on student visas." Imposing such a cap "will inevitably drive valuable students away" from British universities, it said.