The annual limit on Tier 2 work permits comes into force today (April 6th).
Employers will now only be able to use this route to bring in 20,700 people a year from outside the European Union.
A further 1,000 UK visas will be made available to people of 'exceptional talent', but any other overseas workers will have to come through the Intra Company Transfer route, which is not subject to the annual limit.
This UK visa route will, however, also be altered. Only people on the graduate occupation list will be permitted; only those paid £40,000 of more will be able to stay for more than a year, while those paid between £24,000 and £40,000 will have to leave before 12 months and will be unable to reapply within a year of their departure date.
Commenting on the changes, UK immigration minister Damian Green said: "The new system was designed in consultation with business. We have made clear that as the recovery continues, we need employers to look first to people who are out of work and who are already in this country."
He added that the limit is designed to help reduce immigration to sustainable levels while protecting businesses and institutions that are "vital" to the country's economy.
However, a number of businesses and professionals have expressed concern at the dramatic reduction in Tier 2 work permit numbers.
Entrepreneur James Dyson, for example, recently told BBC Radio 4's The World This Weekend that he is "extremely concerned" about the UK's lack of engineers.
According to the inventor, England is under-producing the number of engineers it needs by 50 per cent and the changes to UK immigration will make it harder to source this talent from abroad.