Scottish Power has been named the worst provider when it comes to call centre waiting times.

Customers were left hanging for an average 21 minutes and 24 seconds before speaking to a call handler. However, on some occasions, it took more than 30 minutes before callers got through.

This is in complete contrast to last year when Scottish Power was the fastest of the big six energy suppliers.

Consumer champion Which? made 432 calls to 36 energy firms. Each supplier was called 12 times on different days and times.

While Scottish Power had the longest average wait time, Bulb Energy customers had the longest single call waiting time of 41 minutes and 48 seconds. Overall it averaged 19 minutes and two seconds before calls were put through to a human. Again, Bulb has fallen in the rankings as two years ago it scooped the top spot for the quickest call handling times.

At the other end of the scale So Energy was the fastest this time round, with the average call wait time coming in at just 38 seconds.

This was followed by Ampower, Ebico, Flow Energy and Together Energy which all answered calls in less than a minute.

Of the largest six energy suppliers, EDF took the top spot, answering calls in three minutes and two seconds on average.

Live web chat

Which? also compared wait times for live web chat offered by 12 energy companies.

Spark Energy was the fastest to respond, taking just 30 seconds on average. Outfox the Market, Scottish Power and Utility Point also responded to live chat in under a minute, on average.

Energy giant British Gas was the slowest company to respond to live chat queries with an average wait of seven minutes and 14 seconds. In fact, it’s quicker to call the provider as it averaged four minutes and 19 seconds on average.

Bulb and Utilita’s live chat platform was unavailable 11 out of the 12 times researchers attempted to test it.

Natalie Hitchins, Which? head of home products and services, said: “Energy customers should be able to expect good customer service from their supplier, so it is unacceptable that some people are facing waits of half an hour or more just to speak with an adviser.

“If you are tired of poor customer service and wasted time on the phone, then you should switch to a provider that can better meet your needs, and potentially save you hundreds of pounds.”

YourMoney.com has contacted Scottish Power for comment.