This year the average UK household gas and electricity bill has risen by nearly 40 per cent. While more and more families struggle to pay their energy bills, are the big companies that dominate the domestic market making millions in profit for themselves and for their shareholders? They say they have no choice but to pass on their rising costs to the customer, but is this the truth? Dispatches reporter Deborah Davies investigates why our charges are so high and how much the companies make from estimating bills.