The latest quarterly energy complaints data from the consumer body shows that complaints have risen by nearly 50 per cent to an average of 271.3 per 100,000 customers between January and March this year from 159 between April and June last year.
Only EDF has a lower level of complaints, down to 76.8 from 82.7.
SSE is still the best performer, although its complaints have risen by 21.4. Scottish Power is still the worst performer with 1,154.6 complaints, up from 256 following the introduction of a new billing system last summer which has resulted in a huge rise in complaints for the company.
A Scottish Power spokesperson said: “The end of 2014 and the beginning of 2015 was our most challenging period following the introduction of a new £200 million customer IT system. In the long-term this major investment will ensure that our customers can fully benefit from the upcoming rollout of smart meters. During this period we were set tough improvement targets by Ofgem, and we recruited over 700 frontline customer service advisors.
“In recent months we have significantly reduced the number of complaints received, which will be reflected in future surveys. We are fully committed to continuing with our improvements and providing the best levels of customer service possible.”
Complaints for British Gas rose to 83.9 from 81.4, while E.on’s rose to 101.1 from 79.2. Npower saw complaints increase from 599 to 675.4 per 100,000 customers.
Citizens Advice’s chief executive Gillian Guy said: “Energy firms have no excuse for continued poor service. The majority of complaints from customers are about their bills. With billing a basic part of the service energy firms provide, it should be the simplest thing to get right.
“While Scottish Power and Npower have taken steps to tackle their ongoing billing problems, which have caused a huge number of complaints, some customers are still finding it difficult to get their problem resolved.
“The CMA has made encouraging interim recommendations to improve this market. It now needs to act to ensure all customers get the best deal and good customer service from suppliers.”
Earlier this week Ofgem secured free energy and a clearing of outstanding debt for 1,000 Npower customers until their complaint is resolved after the supplier failed to provide a final resolution to their ombudsman complaints within the allowed timeperiod.