MPs can force UK to keep ban on prisoner votes - minister
Justice Secretary Chris Grayling has told MPs they could vote to defy a European Court of Human Rights ruling and keep the ban on prisoners voting.
But Mr Grayling said there would be a "political cost" in doing so.
He was speaking as he unveiled options in draft legislation to allow some prisoners to vote.
A spokesman for the Council of Europe, which oversees the court, called on the UK to "move forward" and comply with the ruling.
MPs voted in February to keep the ban, but Mr Grayling said he took his obligation to uphold the rule of law in this case "very seriously".
In a Commons statement, Mr Grayling said the draft bill contained three options: keeping the existing blanket ban; giving the vote to convicted prisoners serving up to six months; or giving it to those serving up to four years.
The bill will now undergo detailed pre-legislative scrutiny by a parliamentary committee, and Mr Grayling said he could not be sure when the options would be put to a vote in the Commons.
The BBC's deputy political editor James Landale said a draft bill would take a long time to consider and was unlikely to be presented to Parliament as part of a government legislative programme until May 2014 when the proximity of an election - scheduled for May 2015 - could cast doubt on its future.
Because Parliament was sovereign, Mr Grayling said, MPs could decide to "legislate contrary to fundamental principles of human rights" with the constraints against doing so "ultimately political and not legal".
But he warned that, prior to any final decision, "Parliament must squarely confront what it is doing and accept the political cost".
Nils Muižnieks, Human Rights Commissioner at the Council of Europe - the body that oversees the European Court of Human Rights - disputed Mr Grayling's analysis.
"The UK decided to delegate some small part of its sovereignty to the Council of Europe when it joined and when it agreed to abide by the rulings of the court," he told BBC Radio 4's World at One programme.
Britain had "a lot of room for manoeuvre" on how it complied with the judgement, but it needed to act, he said.
Shadow justice secretary Sadiq Khan said Labour remained opposed in principle to lifting the ban.
He estimated that there were 30,000 prisoners, including 4,188 burglars, who could get the vote under one of the government's proposed options.
"So much for this government being on the side of innocent homeowners," he remarked.
It was "absurd" to believe that the lifting the ban would cut re-offending rates or make it easier for ex-prisoners to re-integrate into society, he argued.
"That being said, we respect the rule of law and we will uphold it," the shadow justice secretary added, prompting laughter from government backbenchers.
At the moment, only prisoners on remand are entitled to vote.
The prime minister has said the prospect of enfranchising others makes him feel "physically ill", and the vast majority of MPs from all parties want to see the blanket ban maintained.
But Lib Dem peer and Justice Minister Lord McNally said he believed that it "could be possible to devise a system of enfranchisement of some prisoners that could play a useful part in a rehabilitation process".
In the House of Lords, Lord McNally warned that MPs should take "full account" of the fact that "setting a precedent where it is optional whether you comply with a convention and the court" could reduce the amount of pressure ministers could bring to bear on countries with worse human rights records than the UK.
The UK has been on a collision course with Strasbourg since 2005, when the European Court of Human Rights (ECHR) ruled that the ban was a breach of human rights, following a challenge by convicted killer John Hirst.
As part of its obligation as a signatory of the European Convention on Human Rights, the government must make clear by 16:00 GMT on Friday how it intends to comply with the judgement.
The Council of Europe - which oversees the ECHR - has said the UK is obliged "to introduce legislative proposals to amend the electoral law imposing a blanket restriction on voting rights of convicted prisoners in prison and achieve compliance with the court's judgement".
In February, MPs voted by 234 to 22 to keep the blanket ban, in response to a government proposal to give the vote to offenders sentenced to a custodial sentence of less than four years.
The coalition subsequently indicated it would respect Parliament's wishes by doing the minimum needed to comply with the ECHR ruling.
The BBC's legal affairs correspondent, Clive Coleman, said not complying with the EHCR could lead to thousands of compensation claims by prisoners.
"That would be hugely politically embarrassing for the government, but it may feel that that's a price worth paying for standing firm in the face of the European court's ruling.
"Those claims could go on in perpetuity - it could literally be the tap that never stops running. We've got 86,000 prisoners in the UK, it could be a lot of public money in legal payments and legal fees."
The draft bill is understood to refer not just to prisoners' voting rights in general and local elections in the UK but also to elections to the European Parliament.
This is because ministers are mindful of a case before the Supreme Court of England and Wales.
George McGeoch, who is serving a life sentence for murder, is arguing that his rights as an EU citizen are being infringed because he will not be able to vote in the 2014 European parliamentary elections.
Should the Supreme Court decide to enfranchise Mr McGeoch, that would automatically allow thousands of other convicted prisoners around the UK to vote in European and municipal elections and open the door to retrospective compensation claims.
It is believed the government hoped the draft bill would delay - and ultimately sway - any decision by the Supreme Court.