New data from Citizens Advice shows the gap between the best and worst energy suppliers for -handling customer complaints has increased.

The results for July to September 2015 are from the Citizens Advice quarterly energy supplier league table. For the second time, this includes customer complaints data from the 19 largest energy suppliers operating in Great Britain.

Co-operative Energy was ranked lowest. It has the highest customer complaint ratio ever recorded by the watchdog after it introduced a new billing and customer service system.