Peers heard a statement by Liberal Democrat Justice Minister Lord McNally on prisoner voting on 22 November 2012, in which he appeared to put himself at odds with the Conservative justice secretary over whether to give inmates the vote.
The government has brought forward draft legislation on whether to extend the franchise to prisoners following a European Court of Human Rights ruling that a blanket ban was unlawful.
The bill contains three options: maintaining the status quo, allowing inmates serving less than six months, or extending the franchise to those sentenced to four years or less.
At present, the only prisoners allowed to vote in the UK are those on remand. But the ECHR ruled in 2005 it was a breach of human rights to deny prisoners a vote.
The government was given until 16:00 GMT on 23 November to respond to the ruling.
MPs voted in February to uphold the ban, and both Justice Secretary Chris Grayling and Prime Minister David Cameron have said they are opposed to extending the vote.
After the statement was repeated in the Lords, the deputy leader of Lib Dem peers, Lord Dholakia, asked Lord McNally: "Do you accept that by granting the right to vote it does help the process of rehabilitation of offenders?"
He replied: "The secretary of state set out his personal view and the prime minister's personal view and I personally share your view that it could be possible to devise a system of enfranchisement of some prisoners that could play a useful part in a rehabilitation process."
Justice Secretary Chris Grayling has said Parliament has the right in law to tell the European Court of Human Rights (ECHR) that it does not accept its ruling, but said there would be "consequences" for the UK's position in Europe if MPs chose to defy the judgement.
The statement was made first in the Commons by the justice secretary.