Government plans to make migrants pay a ''health surcharge'' as part of their visa application could cost the NHS more in the long run, academics have warned.
Anyone from outside the European Economic Area (EEA) coming to the UK for longer than six months is now required to pay a £200-a-year fee, which the Department of Health said would ensure they make an "appropriate financial contribution to the cost of the health services they may use".
Writing in the BMJ, Lilana Keith of the Platform for International Cooperation on Undocumented Migrants in Brussels, and Ewout van Ginneken, a senior researcher at Berlin University of Technology, said that the Government wants the public to believe the country will become less appealing to undocumented migrants and will save taxpayers' money, but "this view is shortsighted and misleading".
They said that the estimated 618,000 undocumented migrants living in the UK - who would not have paid the surcharge - contribute to the economy through their employment, from buying goods and services, and may even pay or have paid income tax.
"They are not free riders in the NHS but contributors," they wrote. "Not providing them with coverage is unfair as well as contrary to their rights as human beings."
They point out that denying those that have not paid the surcharge access could cost more, as emergency services, which must be provided at the point of need, are far more expensive than preventive or planned care and the NHS can rarely recoup these costs from patients who do not have the means to pay.
They said that not having access to preventive services could also lead to outbreaks of infection or disease at a far greater cost to the health system and wider society.
Thirdly, evidence shows that undocumented migrants are healthier, cost less to cover, and use services they are entitled to less than nationals, they said, citing examples of Sweden and Spain as recently finding this.
Finally, they said the administration of charging migrants is in itself a major burden on the NHS.
"Health professionals have also expressed concern over being expected to act against their professional ethics and act as border guards," they added.
The pair quoted a recent Doctors of the World report, which found that only 2.6% of respondents cited health problems as a reason for migration.
"No other EU country has such a structural link between immigration applications and access to health services," they wrote.
They said it has also been suggested that undocumented migrants should be charged for emergency and primary services, which would make the UK's healthcare system "among the least accessible in Europe".
"Rather than holding a public consultation on extending these charges to emergency and primary care, as the freshly elected Conservative government plans to do, the evidence indicates that the opposite approach would serve the UK and its NHS better," they wrote.
"They should explore ways to provide non-discriminatory access to the NHS for all."
The new measures were implemented in April, as part of plans which the Government said will help recoup up to £500 million a year by the NHS by 2017/18.
They see patients being asked questions about their residence status in the UK whenever accessing a new course of treatment, and if there is uncertainty about their residence status, they may be required to submit documentation including passports and immigration documents.
Hospitals receive an extra 25% on top of the cost of every procedure they perform for an EEA migrant or visitor with a European Health Insurance Card (EHIC), while short-term visitors from outside Europe will be charged 150% of the cost of treatment.
The Department of Health also previously said it is looking at piloting ways the NHS could recover costs from international visitors seeing GPs.
A Department of Health spokesperson said: "We disagree with this report. We need to make every NHS penny count, and our plans will recover up to £500million by 2018, offering taxpayers a fairer deal."