Ofgem has banned small energy supplier Iresa from taking on new customers until its problems with customer service has been resolved.

It has ordered the company to extend call centre hours, bringing down average call waiting times to below five minutes and responding to customers who request a call back by the end of the next working day as well as reply to customers emails within five working days.

The supplier has also been urged to log and record all expressions of customer dissatisfaction as well as manage and identify vulnerable customers, including offering to put them on a priority services register.

Ofgem said it will take further action, including ultimately revoking Iresa’s licence, if the issues are not resolved within three months.

It has also banned the company from increasing existing customers’ direct debits and asking them for one-off payments.

Dermot Nolan, Chief Executive of Ofgem, said: “This order sends out a very clear message to suppliers that where they fail their customers on service, Ofgem will step in and take strong action.

“It’s crucial that all suppliers provide customers with good service, including acting quickly and effectively to sort things out wherever problems occur.”

The regulator continues to run a separate longer term investigation into the company.

Iresa said it is “actively working” to fix the issues raised by Ofgem.

A spokesperson added: “We are confident that our customers will see a noticeable improvement in our customer service response times and we apologise to customers who we have let down in the past. We are committed to improving our quality of service to deliver a much better customer experience.”