Justice Secretary Chris Grayling has said he may have to back votes for prisoners because of his constitutional duty to "uphold the law".
The European Court of Human Rights has told the government to present plans to allow inmates to take part in elections, but most MPs are opposed.
Mr Grayling said his other role as Lord Chancellor meant he was in a "different situation" to other MPs and ministers.
The government and Labour both oppose giving serving prisoners the vote.
Parliament is expected to tackle the issue in the next few months, but Prime Minister David Cameron has vowed inmates will not be given such rights under his government, saying the idea makes him feel "physically sick".
If Parliament chooses to oppose the will of the Strasbourg court it could create an impasse which would strain relations and could involve the UK leaving the European Convention on Human Rights, according to some analysts.
Currently only prisoners on remand can vote, but the court has ruled that a blanket ban on those serving sentences doing the same is illegal.
Mr Grayling told BBC One's Sunday Politics: "When we come to the point of a vote, I will take appropriate legal advice.
"My position is very different to other Members of Parliament on this because of my role as guardian of the judiciary."
Mr Grayling added: "I have a legal responsibility. You can't be Lord Chancellor and Justice Secretary and not uphold the law."
He said: "The requirement upon government and government ministers is very clear, that it's our duty to implement rulings of the European court. But the legal position for Parliament is different."
He added that while Mr Cameron "would have to decide at the time how he wants ministers to vote, my position is different".
Mr Grayling said he had been advised by Attorney General Dominic Grieve that Parliament could overrule the court.
MPs opted in February to keep the ban, although this was in a show of opinion rather than a binding vote.
In a statement to MPs last month, Mr Grayling said that, because Parliament was sovereign, it could "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 Muiznieks, Human Rights Commissioner at the Council of Europe - the body that oversees the European Court of Human Rights - disputed Mr Grayling's analysis, saying: "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."
Britain had "a lot of room for manoeuvre" on how it complied with the judgement, but it needed to act, he said.