The European Commission is reportedly taking legal action against Spain, where it says some hospitals have refused the card which guarantees EU citizens free healtchcare across the continent.
British patients showing the European Health Insurance Card (EHIC) get free treatment from hospitals in any country, with the tab picked up by the NHS. Other countries have similar arrangements.
But the Commission now claims that hospitals in Spain have failed to honour the agreement, telling foreign patients to claim the cost of care back on their travel insurance, according to the BBC.
The Commission has requested information about the refusals from the Spanish government, and the country could be fined.
Meanwhile, the UK could be similarly investigated over the right-to-reside test for EU nationals moving to the country.
The check is said to be discriminatory because it goes beyond the standard eligibility criteria for welfare payments.