Patients faced with "undue delay" on the NHS can go abroad for treatment and have the taxpayer pick up the bill, the European Court ruled today.
The judges made the decision in the case brought by Yvonne Watts, 74, who spent £3,900 on a hip operation in France after being told to wait up to four months on the NHS.
Her local Bedford primary care trust (PCT) had insisted the wait did not amount to "undue delay", and had informed her it would not pay for the treatment as the waiting times fell "within the government's NHS plan targets".
But today the European court of justice said that, according to EU rules on free movement to provide services, a national healthcare system must pay the bill if a patient is forced to go elsewhere in the EU for treatment due to delays.
The court said it was up to British courts to decide whether Mrs Watts had been faced with "undue delay" for her operation, and therefore whether she should be reimbursed.
But the judges made clear that this decision could not be based on the government's targets for waiting lists in the NHS - instead it should be on the basis of how long it was acceptable to wait in the light of an "objective medical assessment" of clinical need.
The Department of Health (DoH) said it would need time to understand the full implications of the ruling, but insisted it did not expect an increase in people travelling abroad to receive hospital treatment on the NHS.
Patients in "certain circumstances" had always been able to claim back the costs of being treated abroad, a spokesman said, after first being authorised by their local NHS healthcare commissioner.
"However, we need to understand the full implications of the court's judgment before we make any changes to the systems operated by the NHS," he said.
"We will incorporate the actions that we need to take in response to today's judgment and will issue updated guidance to the NHS shortly.
"But we do not expect this judgment to make a big difference to the number of persons travelling abroad to receive hospital treatment on the NHS."
The spokesman noted that today's ruling did not decide whether Mrs Watts should be reimbursed, only clarified what factors must and must not be taken into account by the court of appeal when considering what an "undue delay" is.