Justice Secretary Chris Grayling may be forced to support giving prisoners the vote because of a legal wrangle over his dual role, he said yesterday.
Mr Grayling, who is also Lord Chancellor, said it was his duty to uphold the law. Other MPs could vote how they wished.
He said: “When we come to the point of a vote, I will take legal advice. My position is different to other MPs. I have a legal responsibility. You can’t be Lord Chancellor and Justice Secretary and not uphold the law.”
The European Court of Human Rights has ruled the government must present plans for allowing prisoners to take part in elections.