Last November, Ofgem imposed a series of targets on the supplier after an investigation identified numerous shortcomings in the firm’s customer service. Goals included reducing average customer call waiting times to a maximum of two minutes by February 1^st, slashing the number of overdue bills from 75,000 to 30,000 by January 1^st, and clearing all outstanding customer complaints.

While the first two targets were met by Scottish Power, the third wasn’t – as a result, the firm now cannot engage in proactive sales and marketing activities until 16 March. 500 sales division staff will spend the period supporting the firm’s customer service teams.

“The ban illustrates the difficulties Scottish Power is having in delivering the levels of service customers deserve,” said Sarah Harrison of Ofgem’s enforcement division.

“While the targets have driven significant improvements in Scottish Power’s performance, we remain very concerned about how customers are being treated.”

Responding to the news, Ann Robinson, director of consumer policy at uSwitch.com, said that the announcement “shows tough action by Ofgem,” and should “serve as a warning to the industry that customers must be treated fairly.”

“It’s encouraging to see that ScottishPower has made significant progress in resolving its customer service issues, but there is still more to do. With trust in energy companies still at an all-time low, all suppliers should give consumers the quality of service they deserve.”