The UK’s ban on prisoners’ voting rights could be ruled unlawful by the European Court of Justice, which is deciding on a similar case in France.
Convicted murderer Thierry Delvigne claims a ban on him voting in elections violates the European Charter of Fundamental Rights.
The court’s ruling could outlaw Britain’s blanket ban at EU level.
But Prime Minister David Cameron has vowed to ignore the judgement being made on Tuesday.
The prime minister has previously said that the idea of prisoner voting makes him “physically sick”.
The European Charter enshrines the right of EU citizens to vote in European elections.
The European Court of Human Rights (ECHR) declared the UK’s ban on prisoner votes unlawful 10 years ago – a ruling which the UK has ignored ever since.
And it ruled again in February that the rights of UK prisoners were breached when they were prevented from voting in elections.
That case was brought by inmates who were in prison during various elections between 2009 and 2011, and was the fourth time the ECHR has ruled against the UK’s ban on prisoner voting.
The European Court of Justice’s advocate general has said that national governments have a right to set their election rules provided they do not “prescribe general, indefinite and automatic deprivation of the right to vote”.
