Yvonne was able to climb up the stairs after her operation

The issue stems from the case of Yvonne Watts who said the NHS should pay for her French hip replacement.

The High Court said the NHS should generally pay out in such cases, but Mrs Watts' delay had not been too long.

Appeals by the NHS and Mrs Watts against various parts of the judgement will now be considered after the European Court of Justice rules.

In the original High Court judgement, Mr Justice Munby said the current reimbursement system was unlawful because the existence of "undue delay" depended, not on a patient's clinical needs, but on whether a hospital was meeting its waiting list targets.

He said an assertion by Health Secretary Dr John Reid that no patient waiting less than the official 12-month target qualified for paid overseas treatment was incorrect

But he said that Mrs Watts, 72, of Queen's Park, Bedford, did not qualify for reimbursement because she had eventually faced a delay of only three months at her local hospital.

'Queue-jumping'

In a ruling on Friday, three Law Lords backed Health Secretary John Reid's view that decisions on the appeal should be deferred until the European Court of Justice had made preliminary rulings on questions of law.

Counsel for Mrs Watts had said Europe had already considered the main questions raised by the appeal.

But Lord Justice May said the Law Lords were "troubled" by the conclusion to which those decisions apparently led.

He said: "We are not clear that the Court of Justice intended to require that those who wished to jump the queue by having medical treatment in another member state are able, if necessary, by so doing to dictate an increase in what may be an already strained national health service budget; or to force the postponement of more urgent treatment needed by others.

"Reflecting those concerns, we would accede to the invitation to refer questions to the Court of Justice.

"Although this may cause delay, the subject is of very considerable general importance."

Under European Community law E112 rule, any EU citizen suffering so-called "undue delays" in receiving treatment in their home country can apply to have the operation in another member state.