A loophole in the system allowing people to charge the NHS for their health treatment in other European countries does exist, but abuse of it is not widespread, the Department of Health has said.
Europeans can have treatment in their home country 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 found.
The card is supposed to be issued to people from within the European Economic Area as well as Swiss nationals who are "ordinarily resident" in the UK, but was given to a Hungarian woman who had visited the UK for less than a day, the paper said.
The woman went back to her native country where she was told by a number of clinics and hospitals that she could avail of certain treatments and maternity care paid for on the NHS, it reported.
A spokeswoman for the department said they accept that it has happened but do not think it is widespread.
Health Minister Alistair Burt, said the situation is "completely unacceptable".
"It is completely unacceptable that people living outside the UK think they can abuse our NHS," he said.
"That's why this Government has already introduced tough measures to clamp down on migrants using healthcare without making a contribution, to save half a billion pounds within a few years.
"We are continually looking at ways we can tighten up the process further, and as a result of this investigation 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."
To get a card, according to the site, a person must be "ordinarily resident" in the UK, meaning that they normally live there apart from temporary or occasional absences.