The European Commission has unveiled a healthcare package designed to make it easier for patients to get medical treatment elsewhere in the EU.
Under the proposals, patients would not have to get their doctor's approval for non-hospital care abroad.
The European Parliament and EU governments must approve the rules for them to take effect.
Patients would be able to claim up to the amount their treatment would have cost in their home country.
The Commission's draft directive is part of a wider "renewed social agenda" package aimed at clarifying citizens' rights in line with European Court of Justice rulings. The package also includes measures to improve access to jobs and fight discrimination and poverty.
In recent years the court's judges have ruled that freedom to cross EU borders for the best and quickest treatment is a right for all.
A Commission healthcare spokesman, Nicholas Fahy, said the aim was to clarify patients' rights to treatment abroad, and the Commission was not introducing new rights.
In a landmark ruling in 2006, the European Court said the UK's National Health Service should reimburse a woman for a hip replacement operation she had in France.
The woman, Yvonne Watts, won the argument that patients facing "undue delays" in the queue for operations should be entitled to treatment in other EU countries. She paid £3,900 for the operation.
No free 'health tourism'
The Commission says patients are entitled to be reimbursed for treatment that their home health authority would normally provide. The NHS would not be expected to pay for spa treatments in Germany, for example.
A UK Department of Health spokesperson said the Commission's proposals "will be subject to change during future negotiations".
"The government is clear that health tourism will not be funded by the NHS," the spokesperson continued.
"We are also absolutely committed to ensuring that, where UK patients choose to travel abroad for care, the NHS retains the ability to decide what care it will fund. Equally, anyone from other member states travelling to the UK specifically for healthcare will have to pay the full NHS cost of treatment upfront."
Currently, only 1% of healthcare budgets are spent on cross-border healthcare and the number of people seeking treatment abroad is very small, the Commission says.
The new package still allows member states to require that their citizens get prior authorisation for hospital treatment abroad. But such authorisations would be on a case-by-case basis, and states would have to prove there was a specific problem justifying their limitation of a patient's right to foreign healthcare.
If the cost of treatment abroad exceeds the cost of similar treatment at home, the patient will have to pay the difference, under the Commission's scheme.
Currently the European Health Insurance Card (EHIC) provides emergency care across the EU for patients who fall ill while abroad. It only applies to those who have health insurance at home.
The new scheme is designed to help in cases where the nearest hospital or specialist clinic is in a neighbouring country, or where a particular treatment can be provided faster or more expertly abroad.
The package is seen as an effort to give patients greater freedom in choosing where they get treatment, and to answer critics who say the EU is too remote from ordinary citizens' concerns.
Mr Fahy said it could take three years for the draft directive to become law through the EU co-decision process and "there is much discussion yet to be had over the details".
The British Medical Association said the proposals "must not be allowed to erode the fundamental values of universality, accessibility and equality" in healthcare.
The BMA told BBC News that the proposals failed to address continuity of care and communication problems, and the risk of NHS services being financially destabilised.