The Strasbourg-based court decided that the right to vote in elections to the European Parliament should be extended to British citizens living in Gibraltar. The Government said it would seek to amend European law to allow Gibralterians to vote in future European elections.
The judges, whose role is to interpret the European Convention on Human Rights, condemned Britain for denying Denise Matthews, 24, the right to be registered as a voter in the 1994 Euro elections.
Ms Matthews had applied to be registered but Britain does not grant residents of Gibraltar a say in choosing MEPs. The ruling opens the way to enfranchise all Britons in Gibraltar for the European elections in June. But as this would first require a change in EU law it would almost certainly be subject to a Spanish veto.