It is "completely unacceptable" that people who have never paid tax in Britain can allegedly charge the NHS for treatment they receive in their own country, a health minister said.
Europeans can have their treatment paid for by using a free European Health Insurance Card (EHIC), given out to those who say they are living in the UK, a Daily Mail investigation said.
The Department of Health admitted it did not know how much of the £721 million paid out to other countries in Europe in the last five years for healthcare treatment had been claimed by people to get treatments in their native country, the paper said.
The Daily Mail sent a Hungarian woman, who has never lived or paid taxes in Britain, to clinics and hospitals in her home country where she was able to use the EHIC which, the paper said, she obtained after visiting the UK for less than a day.
Those medical establishments confirmed that she could get certain treatments and maternity care paid for on the NHS, the paper said.
Health minister Alistair Burt told the BBC: "It is completely unacceptable that people living outside the UK think they can abuse our NHS.
"The department will urgently carry out more work to include EHIC applications."
The NHS Choices website explains that an EHIC card can enable the holder to get free treatment.
It states: "An EHIC will enable you to access state-provided healthcare in European Economic Area (EEA) countries, including Switzerland, at a reduced cost, or sometimes for free.
"It will cover your treatment until you return to the UK. It also covers treatment of pre-existing medical conditions and routine maternity care, providing the reason for your visit is not specifically to give birth."
The card can be issued to people from within the European Economic Area as well as Swiss nationals.
To get a card, according to the NHS Choices website, a person must be "ordinarily resident" in the UK, meaning that they normally live here apart from temporary or occasional absences.