The Prime Minister said he did not believe Labour would come up with a viable answer on English votes for English laws, suggesting “we may well fall out” over the issue.
But he vowed to ensure Scotland would get promised new powers under any government, even if Labour wins in May.
Speaking on the BBC One Andrew Marr programme, Mr Cameron said: “I don’t think Labour have an answer to this question.
“We, the Conservatives, do have an answer - it was in our 2001 manifesto, it was in our 2005 manifesto, it was in the last manifesto as well.
“Be in no doubt, as Prime Minister I will deliver both. So, you can have Ed Miliband and have Scottish devolution and nothing for the English, or you can have David Cameron where you get Scottish devolution and a proper answer to the English question.”
Mr Cameron said he did not back an English Parliament but instead adapting the voting procedures in Westminster for English-only and English and Welsh issues.
He said: “We need to do that, obviously, not just with English laws but if the Scots are going to have, as we believe they should, the right to set income tax rates you need arrangements in the UK Parliament to make sure there is fairness there as well.
“Either there will be an outbreak of common sense by my political opponents and cross-party consent - I doubt it, I suspect it will be the Conservative Party putting forward at the next election a balanced programme of devolution for both Scotland and the rest of the United Kingdom, and when we win our majority we will put that into place in tandem and at the same time.”