More than 4m customers are paying too much for their electricity in areas where there is not enough competition between suppliers, according to Ofgem, the energy regulator.

Presenting the initial results from an inquiry into retail energy markets launched in February, the regulator said it was confident there was no collusion between suppliers to fix prices, either explicit or implicit. Nevertheless, it uncovered areas where it believed competition could be strengthened – the most glaring being the prices paid by electricity customers who were not connected up to the gas grid, generally in remote rural areas.