Energy prices need to be frozen for almost two years because utility companies are "overcharging people", Ed Miliband has told Daybreak.
The Labour leader had written to energy companies to encourage them to "make yourself part of the solution" and build public confidence.
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.