The Prime Minister's official spokesman said Ofgem has given "a very strong signal" that energy companies will not "get away with" bad practice after the it fined ScottishPower £8.5 million.
Asked if David Cameron was happy with the level of the fine, he replied:
Those must be, of course, decisions for the regulator but I think it does send a strong signal in response to bad practice that was being looked at here.
More top news
Hundreds of steelworkers will march on Wednesday to highlight the crisis in their industry.
Report from Institute for Fiscal Studies warns that a Leave vote could cause public finances to take a hit of up to £40 billion.
This is the moment a man discovered a "phenomenally grumpy" looking cat just moments after seeing its face plastered on a "lost" poster.