Scottish Power has received the highest number of complaints ever recorded for a UK energy company over the course of three months, new figures have shown.
A total of 1,163 complaints about gas and electricity provider Scottish Power per 100,000 customers were logged in the last quarter of 2014, Citizens Advice revealed on Friday.
It is the highest figure ever recorded against a single supplier, with complaints about the Big Six energy provider attracting a 588 per cent increase last year, the national charity and consumer advocate said.
The Spanish-owned company was banned from proactive sales from 12 days in March after failing to meet customer service targets set by Ofgem. The regulator said Scottish Power also failed to make improvements in its response to complaints.
The figures indicated that Scottish Power’s new billing system triggered the string of complaints, which left some people not receiving a bill and others struggling to have their problems resolved.
However, the charity said it is working with Scottish Power to help tackle the issues and the company has taken steps to deal with the backlog of complaints by hiring more staff, extending call centre hours and setting up a special phone line for vulnerable customers.
SSE (Scottish and Southern Energy) retained the top spot as the least complained-about company, while the figures also showed that complaints about British Gas, EDF Energy and Npower decreased.
Previously, Npower had received the most complaints of the Big Six for the first two quarters of 2014, but was overtaken in the final half of the year by Scottish Power.
However, while Npower had made improvements, it still received 599 complaints per 100,000 customers in the last quarter of last year, making it the second most complained-about company, the charity said.
Gillian Guy, Citizens Advice chief executive, said: “New billing systems are routinely failing energy customers. In the last few years, four of the largest firms have introduced new billing systems and their implementation has caused chaos for consumers.
“Thousands of customers have been hit by delayed and incorrect bills which have resulted in extreme frustration and significant debts. It's encouraging that Npower is now turning the corner, but Scottish Power still has a very long way to go.”