More customers are no longer prepared to put up with poor customer service and 52% of all complainants surveyed had or were planning to switch as a result of their experience. This compares to 44% of domestic complainants and 47% among micro-businesses when we last carried out the survey in 2014. Suppliers with the worst record on handling complaints face the biggest exodus of customers. A majority of npower and Scottish Power domestic customers surveyed who complained (71% and 59% respectively) said that they had or were planning to switch as a result of their experience, as did 63% of medium sized suppliers’ complainants.While Ofgem encourages customers dissatisfied with their supplier’s complaint handling to vote with their feet, as energy is an essential service, suppliers must provide a minimum standard of customer service. Dermot Nolan, chief executive of Ofgem, has today written to all suppliers surveyed to demand an improvement. He has also written to First Utility and Utility Warehouse, who performed next worst in the survey after npower and Scottish Power, asking them to conduct and publish a thorough independent audit of their complaint handling procedures.Ofgem has already taken action over suppliers’ complaint handling. In December last year npower had to pay out £26m as a result of its billing and complaint handling failings. In April this year Scottish Power had to pay out £18m for similar failures following our intervention.