He would not be drawn on whether his party would commit to a buy-back, but hinted that a decision would be made within the next month.
Mr Cunliffe outlined Labour's energy policy at a media conference in Rotorua this afternoon, which was mostly made up of previously announced proposals such as a single electricity buyer to set lower prices for households and business.
He spoke about the rorting of consumers by partially privatised power companies such as Mighty River Power, which last week announced a 84 per cent increase in profit to $212 million.
The Government sold 49 per cent of Mighty River Power, Meridian and Genesis' shares over the last 18 months.
Asked whether he was in a position to commit to buying back these three companies, Mr Cunliffe said: "We'll be saying more about that before the election.
"We've always reserved the right to take action on that issue."
He would not comment further, but said voters would know where Labour stood on the issue before they went to the ballot box.
Labour left aside $100 million in the fiscal plan it released last week. Mr Cunliffe would not confirm whether this money could be spent on nationalising the companies.
In his speech, Mr Cunliffe said power prices had risen 4.2 per cent in the last quarter. Wages would not rise that much in that next three years, he said.
"The message to Kiwis: If there was a recovery, where is your bit?"
