Energy suppliers are keeping their customers hanging on longer than ever while waiting for a response to their queries.
The finding comes from consumer watchdog Which? It found that half of the 16 companies its representatives tried to contact took at average of more than 10 minutes to answer phone calls.
The survey was carried out over 10 days, and involved researchers calling an energy provider's advertised customer service department number 12 times at set times each day.
It was careful to duplicate its last similar test, "so we could compare to see if suppliers had improved," a spokesman said.
"But we found quite the opposite", he added. "On average, 14 out of the 16 energy companies' customer service departments left us waiting on hold for longer than they did when we carried out the same investigation in April."
And the longest recorded waiting time also went up dramatically, from just over 17 minutes to more than 25 minutes.
The biggest utility companies fared among the worst in the survey, with npower the worst of the 'big six' in both tests. But three more of the biggest companies – Scottish and Southern Energy (SSE), Scottish Power and EDF Energy – saw the largest increases in waiting times. All kept the mystery callers on hold for at least 15 minutes.
Which? executive director Richard Lloyd said: "Not only are customers being left waiting on hold for far too long, but it seems to be getting worse.
"With trust in the industry already at rock bottom and consumers being hit by the latest round of price hikes, it's time the energy companies starting putting their customers first."