The difference between the UK's best and worst energy suppliers is becoming more pronounced, according to Citizens Advice.
When it comes to dealing with customer complaints, the best performing supplier, SSE, was 80 times better than the worst, Extra Energy.
The quarterly results are calculated based on how long it takes for energy suppliers to resolve complaints, taking into account the seriousness of the complaint. Common problems included late or inaccurate bills and trouble getting through to customer services teams to solve problems.
It is the second consecutive quarter that Extra Energy has come bottom of the list. Few suppliers significantly bettered their handling of complaints since Citizens Advice's last assessment.
Gillian Guy, chief executive of Citizens Advice, said: "People shouldn’t face a gamble on getting good customer service. The latest league table shows some suppliers are getting much better at sorting out their customers’ problems, but it's disappointing to see others getting worse at dealing with complaints.
"Patchy and unpredictable customer service affects people in many ways - from the financial stress of being hit with a late bill, to the time wasted trying to get hold of a supplier on the phone."
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