According to a ranking of the five cheapest deals, M&S Energy’s Fix & Save came first at £1,139 a year, while Npower’s Online Price Fix October 2014 came second at £1,181 and Scottish Power’s Online Fixed Price Energy November 2014 came third at £1,195.
Which? said it was important that consumers shop around as two popular fixed-rate energy deals from EDF and First Utility end at the end of September.
Earlier this week, energy regulator Ofgem announced that its new standards of conduct were coming into force. These are designed to ensure that energy suppliers treat consumers fairly.
Richard Lloyd, executive director at Which?, said: “Improving the way suppliers deal with their customers is a step forward but Ofgem’s reforms to fix the broken energy market do not go far enough.
“Rising energy bills are consistently one of the top worries for consumers so the government must step in to ensure trust in suppliers is rebuilt and prices are kept in check.
“We want the government to introduce simple pricing and ring-fence energy supply from generation businesses to increase confidence that there is effective competition in the energy market.”