A new investigation into energy price comparison websites has been launched.
Ofgem said it will look into whether some sites have breached competition law in relation to paid online search advertising.
If follows accusations online price comparison sites were hiding the cheapest tariffs from customers in favour of deals which gave them a cut.
This is separate to the investigation launched in February into whether two or more companies providing a supporting service for the energy sector have breached competition law.
Ofgem stated: “For the avoidance of doubt, these investigations do not affect consumers’ ability to use switching sites to get the best energy deal.
“The fact that we have opened these investigations does not mean there has been a breach of competition law.”
Earlier this year the Energy and Climate Change Committee said energy price comparison sites should compensate customers who were not given the cheapest deals on the market.