Ramsay Dunning, general manager at Co-operative Energy said: "It's no surprise to see the Big Six objecting to Ed Miliband's pledge to freeze energy prices from 2015 until 2017. The British energy industry has been in the grip of a stranglehold by these companies for far too long.
"We believe it doesn't have to be this way and something has got to change to help energy customers all over the UK who are not only confused and deprived of any real choice but worryingly for many, unable to pay their energy bills."
As Ed Miliband clashes with the energy giants on prices, it is worth knowing how your expensive energy bills are actually made up.
A leading competition lawyer says an energy price freeze could leave Labour open to challenges from the courts or the European Commission.
Whether or not you approve of a state intervention into industry, there are at least two big potential obstacles for an energy price freeze.