Consumer group Which? has reported an all time high of 1.7 million consumer complaints to the Big Six energy providers compared to 1.48 million in the previous quarter.
The lowest number of complaints reported were to about Scottish Power, recording 13.57 per 1,000 customers for Q1 of 2014, but also the lowest to resolve complaints on the same or following day, with only 50% cases.
Scottish Power said this was down to “legacy issues on our new service platform” and some cases were taking longer to resolve as a result.
The next worst for resolving complaints within 24 hours were British Gas with 79.5%, and Npower within 8 weeks 94.13%.
SSE had the second best complaints record, with 27.6 per 1,000, ahead of British Gas (30.84), Eon (32.76), and EDF Energy (46.14).
Npower had the highest number of complaints, with 83.03 per 1,000 customers, a spokesman said that they were beginning to make progress with complaint numbers down 32% in the last two weeks, but they are committed to resolving difficulties with the new billing system.
Which? executive director Richard Lloyd said: “Yet again millions of customers are being let down by poor service from the big six energy companies. This has to change.”