A Supreme Court judge has lashed out at a European Court of Human Rights (ECHR) judgement forcing the UK to allow prisoners to vote, in an unusual legal attack.
Lord Sumption was speaking after the Supreme Court rejected an appeal by two convicted murderers who were challenging the government's blanket ban on prisoner voting.
In an additional judgement he said: "The Strasbourg court has arrived at a very curious position.
"It has held that it is open to a convention state to fix a minimum threshold of gravity which warrants the disenfranchisement of a convicted person.
"But it has also held that even with the wide margin of appreciation allowed to Convention states in this area, it is not permissible for the threshold for disenfranchisement to correspond with the threshold for imprisonment.
"Wherever the threshold for imprisonment is placed, it seems to have been their view that there must always be some offences which are serious enough to warrant imprisonment but not serious enough to warrant disenfranchisement. Yet the basis of this view is nowhere articulated."
While couched in legal terms, the comment is a direct attack on the decision by the Strasbourg court to rule against Britain's prisoner voting ban.
It came as the latest attempt to secure prisoner voting was also knocked down by the Supreme Court.
In a unanimous verdict, Lord Mance ended efforts to fast-track ongoing efforts to accommodate the ECHR judgement at a parliamentary level.
The two claims tried to sidestep that process by appealing for voting rights on the basis of EU law, rather than human rights law.
But the Supreme Court judges said there was no individual right to vote conferred under EU law in the way there is under human rights law.
Peter Chester, who raped and strangled his niece in Blackpool in 1977, should have already been released but the Parole Board have kept him in jail because he presents a danger to the public.
His campaign for a vote started in 2008, when he joined the electoral roll so he could take part in the European elections.
George McGeoch, who is currently serving life in a Scottish prison, said EU laws allow him to vote in local and European elections.
David Cameron, who previously said the prospect of giving prisoners the vote made him "physically sick", praised the judgement as a "victory for commons sense".
Labour shadow justice secretary Sadiq Khan said: "Labour’s policy is, and always has been, that prisoners shouldn't be given the vote.
"We believe that committing a crime so serious that a judge has deprived you of your liberty means you should also lose the ability to vote in elections. That's why we are pleased with today's Supreme Court judgement."
But parliament still needs to respond to the human rights-based legal case for prisoner voting, which it is likely to do by allowing inmates sentenced to less than either six months or four years to vote.
Parts of the Tory party are livid at the prospect of relaxing the blanket ban, with many holding it up as an emblematic issue highlighting the threat to British legal autonomy from the ECHR.