The government is to press ahead with plans to hold Northern Ireland Assembly and council elections on 5 May.
NIO Minister Hugo Swire said he would bring forward legislation to hold elections to 26 councils on the same day as the referendum on voting reform.
"Combined polls are more convenient for voters and this will lead to financial savings through shared use of many resources," he said.
Some politicians warn three polls on the same day could confuse voters.
Mr Swire acknowledged that it would "present unique logistical challenges".
"However, I am satisfied that the practical risks can be managed and my officials will liaise closely with the Chief Electoral Officer and the Electoral Commission to ensure the identification and early resolution of any potential problems," he added.
A bill setting 5 May as the date for the voting reform referendum is currently passing through parliament.
The referendum on changing from first-past-the-post to the alternative vote was pledged as part of the Conservative-Liberal Democrat coalition deal.