Which? executive director, Richard Lloyd, said:
“This is a watershed moment for the broken energy market and millions of people struggling to cope with spiralling bills.
“The investigation must leave no stone unturned in establishing the truth behind energy prices, and while it takes place Ofgem must continue its renewed, tougher approach to protecting consumers. Energy companies must also not wait for the outcome of this inquiry but make urgent changes now to do better by their customers.
“We need to see radical reforms to Fix the Big Six that will inject more competition into the market and help rebuild trust by giving consumers confidence that the price they are paying is fair.”