A woman seriously injured by an uninsured car driver while on a foreign holiday must have her compensation assessed under Greek law, the Supreme Court has ruled.

The ruling will come as a blow to Tiffany Moreno because it means she can expect a lower award than she would have received under UK law.

Ms Moreno, from Barry, Vale of Glamorgan, had her right leg amputated below the knee after being hit when the car left the road on the island of Zakynthos in May 2011.

The Motor Insurers' Bureau (MIB), which compensates victims of uninsured drivers, has admitted liability but contends damages should be calculated according to Greek law.

It argues that damages in uninsured driver cases should be assessed according to the law in the country where the accident happened in the same way as they would be if the accident was caused by an insured driver.

Five Supreme Court justices agreed and unanimously allowed an MIB appeal against an April 2015 ruling by High Court judge Mr Justice Gilbart that the law of England and Wales should be applied.

The MIB is handling Ms Moreno's claim on behalf of its Greek equivalent, the Greek Guarantee Fund (GGF), under EU law provisions which mean a victim of an accident abroad does not have to pursue a claim directly with a foreign organisation.

The Supreme Court justices - Lord Mance, Lord Clarke, Lord Sumption, Lord Toulson and Lord Hodge - ruled that UK 2003 regulations which give effect to EU Council directives mean that a victim's entitlement to damages must be measured by reference to the law of the state in which the accident has occurred.

In the lead judgment, Lord Mance declared that "the UK MIB's liability to Ms Moreno is to be determined in accordance with the law of Greece".

Lord Mance said Ms Moreno was walking along the verge of a road when she was struck from behind by a vehicle driven by Kristina Beqiri, who neither had a valid driving licence nor, it appeared, any insurance. Beqiri admitted responsibility for the accident.

The judge said: "Sadly, Ms Moreno suffered very serious injuries, which included loss of her right leg, requiring her to use a wheelchair, continuing pain and psychological reaction, as well as loss of earnings."

The judge added: "Ms Moreno's concern is that Greek law would yield a lesser measure of compensation than English law."

But Lord Mance pointed out that UK drivers who had similar unfortunate accidents at the hands of uninsured drivers in other EU countries could fare better than under English law.

He said: "There is, for example, evidence that Irish personal injuries damages can be significantly higher than English, and that Italian law can in fatal accident cases award significantly more (and, if relevant, to a broader range of persons) than English law."

MIB chief executive Ashton West said: "The outcome of this case is that the law for damages will now be applied consistently to uninsured and insured cases.

"Nothing changes the fact that Ms Moreno has been the unfortunate victim of a serious accident with an uninsured driver abroad.

"There is no doubt that she is entitled to damages for her injuries; however, the principle is about using the right law to decide how much to pay Ms Moreno.

"MIB is here to help UK residents with their claims for compensation while at the same time protecting the interests of UK motorists, who ultimately provide the funds on which we rely.

"As this relates to events which occurred in Greece, everything surrounding the claim should be treated under Greek law."