The Government's most senior law officer has urged the UK's highest court to reject challenges by two convicted murderers who are fighting for the right to vote while in prison.
Attorney General Dominic Grieve said the cases of Peter Chester and George McGeoch, which are being heard at the Supreme Court in London, raised "important constitutional questions".
Urging seven justices to dismiss their appeals, Mr Grieve said their cases also raised "important questions as to the proper respective roles of the courts and of Parliament in settling issues surrounding the right to vote of convicted prisoners".
Chester, who is in his 50s, is serving life for raping and strangling his seven-year-old niece Donna Marie Gillbanks in Blackpool in 1977.
He is detained at Wakefield prison in West Yorkshire and the minimum term he was ordered to serve before becoming eligible to apply for parole has expired.
McGeoch, from Glasgow, is serving his life sentence at Dumfries prison for the 1998 murder of Eric Innes in Inverness.
He received a minimum term of 13 years, but due to subsequent convictions, including taking two prison nurses hostage in a siege in 2001, will not be considered for parole until 2015.
Chester's challenge at the Supreme Court follows a decision by three Court of Appeal judges in December 2010 to dismiss his case.
The European Court of Human Rights in Strasbourg has ruled that a blanket ban on serving prisoners going to the polls was incompatible with the European Convention on Human Rights (ECHR), relating to the right to free and fair elections.
The court said it was up to individual countries to decide which inmates should be denied the right to vote from jail, but that a total ban was illegal.
David Cameron told the House of Commons last year: "No one should be in any doubt: prisoners are not getting the vote under this Government."
Under section three of the Representation of the People Act 1983, convicted prisoners are prevented from voting in parliamentary and local government elections - and under the European Parliamentary Elections Act 2002 a person is entitled to vote in European parliamentary elections if he is entitled to vote in parliamentary elections.
In November the Government published the Voting Eligibility (Prisoners) Draft Bill for pre-legislative scrutiny by a joint committee of both Houses.
It has put forward three options - a ban for prisoners sentenced to four years or more, a ban for prisoners sentenced to more than six months and a re-statement of the existing ban.
Mr Grieve told Lords Hope, Hale, Mance, Kerr, Clarke, Sumption and Hughes on the second day of the hearing that the draft Bill was "undergoing parliamentary scrutiny", and that the appeals by Chester and McGeoch raised "broader constitutional questions of responsibility for the future shape" of section three of the Representation of the People Act.
He argued that the Supreme Court was "not bound to apply the Strasbourg jurisprudence", but only to take account of any judgment of the European Court of Human Rights, adding: "This court is entitled to take its own course and should do so where it has sufficient doubt about the soundness of the reasoning adopted by the European Court of Human Rights."
The Supreme Court later reserved its judgment to a date to be announced.