David Cameron appeared to be at loggerheads with his chief law officer after flatly ruling out giving prisoners the vote.
The Prime Minister moved to clarify his position amid speculation that the coalition was preparing legislation on the controversial issue.
Giving evidence to MPs, Attorney General Dominic Grieve said a European Court of Human Rights (ECHR) ruling against the blanket ban "imposes an international legal obligation on us".
But Mr Cameron told the Commons: "No one should be in any doubt. Prisoners are not getting the vote under this Government."
The Premier pointed out that in February last year the House called by an overwhelming margin of 234 to 22 for the blanket ban to be maintained rather than eased in line with the ECHR judgment.
That motion was not binding on the Government, but Mr Cameron signalled that he was ready to hold another vote "to put the legal position beyond doubt".
Speaking at the weekly Prime Minister's Questions session, he said: "The House of Commons has voted against prisoners having the vote.
"I don't want prisoners to have the vote, and they should not have the vote.
"If it helps by having another vote in Parliament on another resolution to make absolutely clear, to help put the legal position beyond doubt, I am very happy to do that."