The comments follow a wave of criticism over the last few weeks from university heads and media, who say the government is using student visa curbs as a shortcut to reducing wider immigration – something that could wipe billions off the economy.

In a study released yesterday, Migration Watch recognised the value of international students, but claimed that student visas had become a “back door” to Britain which was “wide open”.

“If the number of foreign students was allowed to increase still further as the universities wish to see, students could eventually add 90 – 100,000 a year to net migration,” Chairman Sir Andrew Green said. “Taking them out of the statistics would achieve nothing.”

It claimed that the student visas had become a “back door” to Britain

Green’s major contentions are with the UK border system, which he says are weaker than those of major competitors. He points out that the UK neither interviews students before granting visas to ensure they are genuine, nor monitors student departures, unlike major competitors such as the US and Canada.

He adds that the US, Canada and Australia all count students in net migration statistics, although concedes they distinguish them as temporary migrants for administrative purposes – a distinction emphasised by those critical of the UK’s policies.

Major industry bodies such as the Institute of Public Policy Research have hit back at the claims. In a  highly publicised report released last month it argued that the government was including students in net migration figures as a fast track to reducing the current level of 250,000 to the “tens of thousands” by 2015 – a manifesto pledge.

“Migration Watch’s focus on abuse is missing the point that most students are genuine applicants”

Alex Glennie, co-author of the report, told The PIE News: “Migration Watch’s focus on abuse of the system is missing the point that most students are genuine applicants who come to the UK and make an economic contribution.”

She said: “We are arguing for taking students out of the net migration figures and only counting them at the point when they switch into other visa categories and stay.”

She also disagreed with Migration Watch’s claim that a 10% fall in overseas numbers would only hit annual foreign exchange earnings by 0.2%. She points to 2010 estimates by the Department for Business, Innovation and Skills that education exports are worth around £14 billion a year to the UK. “Migration Watch’s estimates sound a bit on the low side to me,” she said.

“The UK would continue reporting migration data to the UN using the international definition of a migrant”

Universities UK agreed abuse needed to be tackled, but Chief Executive Nicola Dandridge said: “We must take genuine international students, who come and then go, out of the definition of net migration equation.

“The UK would continue reporting migration data to the UN using the international definition of a migrant, which is precisely what our major competitors do,” she said.

• An edition of Newsnight broadcast on 20 June on this issue can be viewed here: http://www.bbc.co.uk/iplayer/episode/b01k66wv/Newsnight_20_06_2012/