The House of Commons has been urged to reject a European Court of Human Rights ruling that would give UK prisoners the right to vote in national elections.
In 2005 the court ruled against Britain's blanket ban on prisoners voting, saying inmates must have the right to vote.
Many MPs oppose the judgement, however, arguing that it should be up to Parliament to decide whether prisoners should get the vote, not the European court.
Proposing the motion to support the current ban on prisoner voting on 10 February 2011, senior Conservative David Davis said the concept was simple: "If you break the law you cannot make the law."
Prisoners "have broken the contract with society" and thereby lose all rights to liberty and the right to vote, the former shadow home secretary told MPs.
And he warned that the courts would have to "think again" if MPs voted against extending the franchise to prisoners.
The government opposes the ECHR ruling, which followed a lengthy campaign by killer John Hirst, jailed for 15 years in 1980, who successfully argued in the European court that he was entitled to vote.
But ministers say that unless the law is changed the government could face thousands of compensation claims costing millions of pounds.
Labour former justice secretary Jack Straw, who tabled the motion with Mr Davis, dismissed these fears.
"Unless the Strasbourg court now sees the purpose of compensation as some kind of gratuitous fine on the elected British House of Commons, I fail to see by what algebra or alchemy any court could equate the absence of a vote in prison...with some monetary amount," he said.
He told MPs that the problem had arisen because of the European court's "ever-widening remit", creating a "conflict of principles" between whether prisoners should be allowed the vote and Britain's treaty obligations.
A ban on prisoners voting had been in place in the UK since at least 1870, he said, arguing that it was for domestic parliaments to legislate on such matters.
Part two of the debate, in which MPs vote on the motion, can be found