A £1 saving in individual consumer bills – because the domestic market was more competitive – would more than offset all the costs of a faster switching programme, says Ofgem. It based that on CMA estimates that domestic consumers as a whole paid an average of £1.4 billion a year more than they would have done under well-functioning retail markets in 2012 to 2015.

Publishing its full business case for the programme, the regulator admitted that costs had risen by £94 million to £426 million since it published an Outline Business Case.