The Commons will vote tomorrow on whether to grant prisoners the right to vote.
The government has avoided finding itself in a difficult decision by granting a free vote, in which ministers will abstain and backbenchers are allowed to make up their own mind.
That means a mass backbench rebellion on the issue has been avoided, although privately many ministers agree with Tory MPs planning to defy the European court of human rights' stance on the issue.
Even prime minister David Cameron has said the prospect of granting convicted criminals the vote makes him feel "physically ill".
But failure to comply with the 2005 ruling by the ECHR, which said the UK's blanket ban on prisoners' voting was unlawful, could cost the Treasury £100 million in compensation claims from prisoners.
There has been fierce opposition from both sides of the aisle to the prospect of giving prisoners the vote, especially people serving longer sentences for hard crime.
The government has said it would apply the ruling to as few prisoners as possible, but it is unclear where ministers would draw the line.