LONDON, England - Britain's interior ministry Sunday said its plans to tighten the visa system for foreign students would not damage the country's universities.

An alliance of chief executives from 16 universities has written to the interior minister, Home Secretary Theresa May, urging her to abandon plans to restrict the number of visas and impose strict English language requirements.

Students represent almost two-thirds of non-European Union migrants coming to Britain.

The government thinks the system is wide open to abuse, with obscure courses and colleges effectively offering a back door to settling in the country.

"Any criticism can only be based on speculation as no decisions have yet been made on the changes to the student visa route," a Home Office spokeswoman said.

"However, universities that are confident in the product they have to offer genuine students should have nothing to fear from policies that root out abuses in the student visa system."

In a letter to The Observer newspaper, the university vice-chancellors expressed their "profound concern", arguing that the government's direction would have a devastating effect on universities' incomes and ability to run the best courses for British, as well as foreign students.

"International students coming to universities contribute over £5 billion ($8 billion, 5.8 billion euros) each year to the UK economy through tuition fees and off-campus expenditure.

"Reductions in student numbers will lead to reductions in income and jobs. Without international students, many university courses, particularly science and engineering courses, may no longer be viable. This will in turn reduce the courses available to UK students."

Immigration is a hot topic in Britain, with an extensive recent poll finding that 63 percent of white Britons thought immigration has been bad for the country.

Feeling the immigration system is largely out of control, Prime Minister David Cameron wants to cut net migration from hundreds of thousands to tens of thousands annually.

Fresh Home Office research last year revealed that of 186,000 foreign students granted visas in 2004, more than one-fifth were still in Britain five years later. Officials fear many may be working illegally.

The number of visas being issued to students and their dependants had risen to more than 300,000 by 2010, the figures showed.