Mark Field is a member of the Intelligence and Security Committee and MP for the Cities of London and Westminster.

“Whenever I travel in the world, particularly in China and India, one question persists,” Professor Andrew Hamilton reflected last month. ‘”Why has the UK adopted a visa system so hostile to student entry?” Frankly, it baffles me too!

As Vice-Chancellor of Oxford University, Professor Hamilton understands both the colossal economic opportunity that international students represent to the UK, as well as the aggressive competition to attract their business from rivals like Australia, Canada and the United States.

Rocketing growth in Asian economies has ensured that tens of millions of Chinese, Korean, Malaysian and Indian citizens will continue to be added to the ranks of the global middle class every year. This affluent new cohort has a hunger for higher education that Asian universities have not yet the capacity to cater for. This creates an exciting opportunity for developed nations over the past decade, similarly hungry to find new areas of growth for their ageing, undynamic economies at a time when state subsidies to universities are necessarily being cut.

It has been a match made in heaven – with the considerable added bonus that a sustained flow of international cash and top postgraduates and academics into universities helps to grow associated high value sectors such as science, technology and engineering. In the UK this has created a virtuous circle, allowing the talented to cross-pollinate and combine with money and commercial opportunity.

But that delicate ecosystem is now under threat. Asian nations understandably want to retain the talent on their own soil and are resolutely building up their higher education institutions. Competitor states like Australia and Canada, meanwhile, want to increase their slice of the action.

Depressingly, the British response to this has not been to up the ante. Instead, we have allowed a debate about the number of immigrants in our country to morph inadvertently into a crackdown on the flow of international talent into our universities, impeding one of the most important growth industries we have. That Professor Hamilton’s lament has been echoed by Nobel prize-winning scientist, John O’Keefe, who warned that the system was now creating a “very, very large obstacle” to recruiting top global scientists, should make sirens go off in the corridors of power.

Officially, the Home Office places no limit on the number of students who can come to our shores to study with visa allocations in place for academics. Reality suggests, however, that the cumulative effect of the Government’s immigration policies, coupled with the hostile tone of public debate on immigration, are acting to deter the best post-graduate students and academics from signing up even to our elite institutions.

Over the course of its term, the coalition has implemented a stricter, more complex and more costly visa regime for non-EU students. Restrictions on the routes into employment have been imposed that make it difficult to find meaningful job opportunities for those keen to develop their early careers once their courses end.

The Government has recently legislated, via the Immigration Act, for students and academics to pay fees upon entry for the NHS (not an insignificant annual sum for a PhD student staying for a few years with his or her spouse and children). Yet the tone of debate on immigration has toughened as Ministers (and Shadow Ministers) have increasingly appeared to dance to UKIP’s tune. When prospective students calculate the cost of visas, upfront health and rent payments and high academic fees, then contemplate the bureaucratic complexity and sense of general public hostility, they will ask a simple question: “Do other nations hold out a more attractive offering?”

This is perhaps why in 2012-13 we saw the number of international students coming to the UK to study at higher education institutions decline for the first time ever. This included a precipitate and worrying decline in Indian students coming to the UK between 2011 and 2013. Troublingly, these falls are most profound among the postgraduate population, with a drop in numbers of 2.8 per cent between 2010-11 and 2012-13.

Since non-EU students tend to focus on subject areas like engineering, computer science and maths, where they will often outnumber UK and EU students, this postgraduate contingent is particularly critical to the viability of courses in some of the areas where the UK wishes to maintain a cutting edge. The Russell Group has regularly pointed out that the combined teaching income for so-called STEM subjects does not cover the average annual cost of teaching that resource-intensive subjects require, so that UK and EU students are taught at a loss. This makes the continued supply of international students essential to the basic economic viability of undergraduate STEM teaching in even the most prestigious universities.

These concerns are raised time and again by the elite universities in my own constituency. At Imperial College, recently placed joint second in the world university rankings, 40 per cent of doctoral research postgraduates come from outside the EU. In 2012/13, Imperial received over double the sum of home and EU students’ fees in academic fees from overseas students (£103.8 million versus £48.2 million).

Indeed, this leading global institution calculated that for every lost international student, two and a half home students are required to make up the fall in income. The UK’s elite educational institutions wish to see the flow of students removed from net migration figures, with students and academics excluded from payments for the NHS and post-study routes into work reinstated. They also seek policies that think holistically about how enhance the UK’s attractiveness in terms of scientific and technological innovation.

When high-flying education consumers turn their backs on the British offering, the damage goes way beyond the loss of income from the individual student. There is the cost of lost opportunity, whether from the new generation of global ambassadors that we failed to foster or the research scientist that did not get the chance to find the next big breakthrough in the UK. There is also harm to the domestic offering to British and EU students, whose courses are often significantly subsidised by the academic fees of their international counterparts, particularly in specialised postgraduate courses. Small wonder that our competitors in this lucrative market are licking their lips at the prospect of the UK becoming a more unappealing financial and social proposition.

Britons relish our reputation as a world-leader in the high-end technological and scientific innovation that often begins with a breakthrough in the university lab. Britons are proud of our consistently high rankings in the university league tables. But in today’s world, an enviablebrand such as this can only be sustained if we accept that the brightest minds must be given easy passage here. All polling evidence confirms that unease on immigration does not extend to students and academics, or at least beyond the bogus language colleges, which this government has been so effective at closing down. So let us not only recognise that but challenge and support our higher education sector to increase the UK’s share of this high quality, lucrative and rapidly expanding market.