Npower was rated the worst for complaint handling and customer service, scoring a meagre 35 per cent, closely followed by Scottish Power with a score of 41 per cent. EDF and British Gas scored slightly higher with 49 per cent, while Eon and SSE both scored 50 per cent.
Spark Energy was the only small supplier to score as low as the big six with 50 per cent.
Meanwhile, Ecotricity ranked highest with a score of 84 per cent, followed by Good Energy (82 per cent), Ebico (81 per cent), Ovo Energy (80 per cent) and Utility Warehouse (76 per cent).
The big six were recently chastised by Ofgem for “frankly awful” customer service and ordered to publish independent audits of their process for closing complaints by the end of November 2014.
Which? executive director Richard Lloyd said the big six need to “up their game” if they want to help restore trust among their “long-suffering” customers.
Recent research from Which? revealed that overall customer satisfaction with UK energy companies has increased from 41 per cent to 48 per cent in the last year. However, this score is still low compared with other sectors.
Data from the latest Which? consumer insight tracker reveals that only 20 per cent of customers trust their suppliers, causing more people to “turn their backs” on the big six and joining independent providers.