Extra Energy has been voted the energy supplier with the worst customer service for the second time.

It was awarded the lowest score on Citizens Advice’s star rating system, receiving 2.05 stars for the January to March period, down from the 2.5 stars it received between October and December 2016.

In terms of complaints handling, Extra Energy delivered the worst score recorded (1,916 per 100,000 customers) for the period between January and March.

The supplier also received low scores when it came to billing and ease of contact, scoring two out of five for each category.

Common complaints included customers being unable to get through to the company to give meter readings, with others being charged twice for the same bill.

Citizen’s Advice reported some people have also had problems with back-billing – it says one customer received an unexpected bill for £4,500 after 18 months of Extra Energy failing to collect payments.

However, the company did receive full marks for switching, by successfully carrying out 99% of energy switches within three weeks.

Ecotricity scored the highest mark overall, with 4.4 stars. E (Gas and Electricity) and Flow Energy followed closely after, with scores of 4.1 and 3.9 respectively.

In terms of the Big Six, EDF and SSE scored the highest with 3.75 stars, while npower scored the least with three stars.

Ben Jones, Managing Director of Operations at Extra Energy, said: “We’ve always been honest and transparent about the growing pains we experienced, which occurred during a period which saw our customer numbers expand rapidly due to the market leading tariffs we were offering.

“But we’ve also always been clear that we are making unprecedented investments to overcome these issues for good.”