Jeremy Corbyn will consider campaigning to give prisoners the right to vote if he becomes Labour leader.
The Labour leadership candidate said he would follow demands by the European Court of Human Rights to allow convicted criminals the right to vote in British elections.
The court has ruled four times that Britain should lift its ban on prisoner votes but Parliament has refused to give way over the issue.
The 66-year-old left-wing politician supports the principle of overturning the historic ban on jailed convicts voting because he thinks it will help rehabilitate them.
MPs voted in 2011 to keep the ban on prisoner voting, despite the tough stance adopted by the European judges since 2005.
A spokesman for Mr Corbyn said: "On the issue of prisoner voting, we are guided by the European Court of Human Rights."
His comments come as he also unveiled plans to consider introducing women-only train carriages in a bid to cut the number of sexual assaults on public transport.
Like that proposal, Mr Corbyn's comments about prisoner votes are likely to come under fierce criticism.
Politicians argued during a debate in 2011 that prisoners had forfeited their voting rights by breaking the law and going to jail.
Two years ago, Prime Minister David Cameron vowed to "clip the wings" of the European Court of Human Rights and said prisoners "damn well shouldn't" be given the vote.
The last of the four rulings by European judges was made in February this year. They argued that the rights of UK prisoners were breached when they were prevented from voting in elections, and called for a change in the law.
The case was brought by inmates who were in prison during various elections between 2009 and 2011.
Both the previous Labour government and Coalition Government failed to legislate -- although various proposals have been debated in an attempt to end the long-running row with the Strasbourg court.
The most recent case concerned 1,015 prisoners, a grouping of long-standing prisoner voting cases, and the court ruled there had been a violation of Article 3 of the first protocol to the European Convention on Human Rights -- right to a free election.
The February case was brought by convicted killer John Hirst, who has since been released after serving 25 years in jail.
A Ministry of Justice spokesman said: "The Government has always been clear that it believes prisoner voting is an issue that should ultimately be decided in the UK."