Energy firms facing gas price review
Ofgem is to investigate recent rises in domestic fuel bills - after it found the amount of profit made by some energy companies increased sharply in just a few months.
The watchdog said that the net profit margin of £65 per typical customer in September was now £90, a 38% rise.
Energy UK, which represents the major energy suppliers, said it had "nothing to hide" during a review. Christine McGourty, director of Energy UK, told the BBC: "We believe in an open, fair and transparent market".