Theresa May is set to scrutinise the number of student visas being granted to UK university applicants in a fresh attempt to reduce immigration.

The Prime Minister is reportedly preparing her new government to crack down on higher education institutions, claiming they have become an easy route into Britain for economic migrants.

Government sources have said the Home Office and Department for Education will examine the student visa regime to see where criteria can be tightened, according to The Telegraph.

As Home Secretary, Ms May attempted to limit the number of visas for students coming to study on further education courses.

In a confidential letter to other ministers, she also argued universities should "develop sustainable funding models that are not so dependent on international students".

But she could have wrongly deported up to 50,000 international students after an English test cheating scam at one school was used to incriminate all who had sat the test.

The Upper Tribunal (Asylum and Immigration) ruled in March the then Home Secretary’s evidence suffered from “multiple frailties and shortcomings”.

Mostafa Rajaai, International Officer for the National Union of Students, told The Independent: "Thanks to Theresa May's approach to international students while she was in charge of the Home Office, we have witnessed, for the first time in 30 years, a drop in the number of international students coming to the UK. This is while the number of internationally mobile students has been rising year on year.

"While the inquiry into May's actions in response to the 'ETS scandal' is ongoing, she is preparing to devastate more lives by raising feelings of suspicion and distrust.

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"As it stands, the British student visa regime is one of the toughest and least welcoming in the world. By tightening it further, the Higher Education sector will lose out on hundreds of thousands of international students choosing other countries over the UK."

Among the actions being considered are preventing universities from marketing their courses as opportunities for students to work in Britain, tighter controls on so-called “Mickey Mouse” degrees at poor performing universities and further protocols to ensure foreign students return home after finishing their studies.

Ms May last week reaffirmed her target of reducing “net migration” to below 100,000, a goal that David Cameron roundly failed to achieve.

As Chancellor, George Osborne and officials in the Department for Business, Innovation and Skills tried to resist her efforts because they viewed international students as beneficial to the economy and for universities, given their higher rate of tuition fees, calling for students to be removed from official immigration statistics.

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When she became Prime Minister, Ms May sacked Mr Osborne and closed BIS, moving universities under the remit of a revamped Department for Education.

The economy would gain £1 billion from the extra 55,000 foreign students would be coming to Britain every year, according a government report.

The Home Office has estimated one in five foreign students overstays their visa.