At present, the Election Commission allows a number of documents, including passport, as identity proof in the absence of voter ID card.
"Today, we are having too many cards leading to so many complications. Don't introduce too many complications in the system. Time has come we should think of only one card, whatever be the card," Mr Krishnamurthy said.
"ID proof may be Aadhaar card when you are using it for all other purposes. It can be used for election also," he said.
"Aadhaar itself can be made as an election ID card. Why do you want to have election ID card as well as Aadhaar? If all voters are covered by Aadhaar, then you should eliminate voter ID card and make Aadhaar the only ID for electoral purposes," Mr Krishnamurthy told PTI.
He said till the entire country is covered by Aadhaar, both the cards should be allowed as identity proof for voting.
"You can set a particular cut-off date, may be 2019 or 2020 or whatever, everybody should have Aadhaar card (for voting)", the former CEC said.
He also said there was no need for the Election Commission to "delink" Himachal Pradesh and Gujarat Assembly polls, and termed it an "avoidable controversy".
Mr Krishnamurthy argued that Himachal Pradesh election could have been postponed by a few days to club it with that in Gujarat.
"I don't know why they should be delinked because it was an avoidable controversy, I thought. There was no need to delink them," the former CEC said.
"When the convention (holding elections to Himachal Pradesh and Gujarat simultaneously) has been so, it could have been easily followed, or even if there was difficulty, the Himachal elections could have been postponed by four or five days," he said.
The EC had on October 12 announced that the Assembly elections in Himachal Pradesh would be held in a single phase on November 9 and the results would be declared on December 18.
The poll panel did not announce the dates for Assembly elections in Gujarat, but Chief Election Commissioner A K Joti had said that the elections will be held before December 18.
On BJP MP Varun Gandhi reportedly terming the poll panel a "toothless tiger", Mr Krishnamurthy said, "There is no power (with the poll panel) to deregister (derecognise parties), but whether it makes it (EC) toothless animal, I don't know."
Mr Gandhi had reportedly said the Election Commission was a "toothless tiger" as it had never derecognised any political party for not submitting poll expenditure details within the stipulated time.
"Yes, there is no power (to derecognise parties), and that power should be available. Law can be amended to say that if you (EC) have power to register, you can deregister a party under certain circumstances," Mr Krishnamurthy added.