LONDON - Thousands of Pakistani students working in the UK could face problems after a warning of tougher measures aimed at restricting the amount of time foreign graduates can stay in Britain on student visas and could force more companies to go abroad. Renowned businessman and vacuum cleaner tycoon Sir James Dyson, who sits on the British Prime Ministers business advisory group, while giving a warning said he was extremely concerned at recent changes which will cut the number of non-EU students in the country. Last week the British Home Secretary Theresa May unveiled plans that could cut the number of foreign students and their dependants coming to Britain by around 100,000 a year. She announced tighter restrictions on how long students could stay in the UK, before and after the end of their courses - including a rule that they must find a job that pays at least 20,000 a year. May said: We will limit the overall time that can be spent on a student visa to three years at lower levels, as now, and five years at higher levels. But Sir James, who also headed an innovation taskforce for British Prime Minister David Cameron, said it was sheer madness to be effectively chucking out skilled engineering graduates from the UK. He told BBC Radio 4s The World this Weekend: I am extremely concerned because already England is under-producing the numbers of engineers it needs by 50%. There are 37,000 vacancies a year and about 20,000 graduates. So already it is very, very difficult to find engineers. I think it is sheer madness to be effectively chucking out graduates who we desperately need. I am afraid what it will end up doing is driving firms like us abroad because we simply cant get people to do our research and development, he added. Sir James said the government had done some of the right things in the budget to encourage research and development but on visas said: Think again on engineering, I dont know about people learning English and that sort of thing, but when it comes to technology give them the visas and keep them here.