The government is reconsidering its ban on prisoners voting after a landmark human rights case brought by an inmate.
The case was heard at the European Court of Human Rights
John Hirst, serving life in Rye Hill Prison, Warwickshire, for manslaughter, went to court when his application to register to vote was turned down.
The European Court of Human Rights ruled British laws that bar inmates from voting breach human rights.
The Department for Constitutional Affairs is "considering the judgement before deciding its next step".
Human rights breach
A statement from the department said: "We have always argued that prisoners should lose the right to vote while in detention because if you commit a crime that is serious, you should lose the right to have a say in how you are governed.
"This judgement questions that position."
The 1983 Representation of the People Act does not allow convicts to vote.
The 53-year-old brought a case in the High Court claiming Section 3 of the act is incompatible with the European Convention on Human Rights, to which Britain is a signatory.
His case was rejected and he turned to the European Court of Human Rights, in Strasbourg, guardians of the Human Rights Convention.
Lawyers for Mr Hirst said he should have the right to vote under the Convention's guarantee to the "right to free elections", the "right to free expression" and "prohibition of discrimination".
The judges delivered a unanimous verdict that denying a prisoner a vote does breach the "right to free elections" set out in the Convention.
There was no need therefore, they said, to pass judgment on the issues of free expression and discrimination.
Hirst pleaded guilty on 11 February 1980 to a charge of manslaughter on the grounds of diminished responsibility.
He was sentenced to "discretionary life imprisonment" and the tariff part of his term - the part relating to retribution and deterrence - expired on June 25 1994.
Hirst remains in jail, because the Parole Board says he could still present a risk of serious harm to the public.
He was awarded £8,000 in costs and expenses by the court on Tuesday.