Britain announced plans on Wednesday to charge migrants hundreds of pounds a year to access its state-run National Health Service (NHS), in a bid to clamp down on so-called health tourism.
Health Secretary Jeremy Hunt also proposed to stop giving visitors from outside the European Economic Area (EEA) free access to general practitioners (GPs).
"We have been clear that we are a national health service, not an international health service, and I am determined to wipe out abuse in the system," he said.
Ministers admitted however that they have no idea of the true cost and impact of migrants on the NHS, and have commissioned an independent audit to report back in September.
The proposals, which have been put out to consultation, are tied to a wider clampdown on immigration by Prime Minister David Cameron's Conservative-led coalition government.
It also published plans on Wednesday to make landlords check the immigration status of tenants, with the goal of making it more difficult for illegal migrants to stay in Britain.
Under the healthcare changes, the government insisted no-one will be denied emergency care and said the treatment of infectious diseases and sexually transmitted infections would remain free.
However, health professionals warned the changes could still pose a public health risk by deterring ill patients from seeking treatment.
"People use the NHS if they've got infections and we certainly don't want to have people wandering around for fear of being charged at the GP surgery," Clare Gerada, chairwoman of the Royal College of General Practitioners, told BBC radio.
She added: "I don't think we should be turning the GP surgery into a border agency."
The National AIDS Trust (NAT) said the plans also threatened to undermine years of work to encourage marginalised at-risk groups to access HIV testing and treatment.
People visiting Britain for less than six months already have to pay for routine hospital care but the changes would mean they also have to pay to visit a GP.
Students and workers staying more than six months would be charged a set fee of at least £200 (235 euros, $300) a year to cover NHS costs when they apply for their visas. This is in addition to taxes used to fund the health service.
The government also wants to boost efforts by the NHS to recoup the cost of treating patients from EEA countries—the European Union plus Norway, Liechtenstein and Iceland.
The health service currently writes off about £12 million a year that could be claimed back from EEA governments, the Department of Health said.
Countries such as Russia and Australia, which have reciprocal healthcare agreements with Britain, will not be affected by the changes.