The energy regulator Ofgem has written an open letter to the Big Six energy companies asking them to explain to customers why their bills have not fallen despite a drop in wholesale energy prices.
But the firms are saying it is more complicated than it would seem because much more than wholesale pricing goes into making up the cost of our bills.
The government said the companies would do well to listen to the letter or face action - the toughest of which would be a full competition inquiry.
More top news
Given how dependent the rest of world is on China, it's $33 trillion debt could affect the UK - and here's why.
"Their fictitious state has fallen," an Iraqi military spokesman said after forces were said to have recaptured the landmark mosque from IS.
The sister of one of the Hillsborough victims said her father made her promise to "get truth and justice" on his deathbed.