Energy firms have been told to contact customers who miss payments as the regulator cracks down on poor customer service standards.

Under Ofgem's rules taking effect on 14 December, suppliers must get in touch with customers who miss two monthly or one quarterly payment to offer support.

They have also been told to prioritise vulnerable customers.

Customer service scores must also be published, in a scheme similar to that used by banks.

The new standards, coming after a summer consultation, aim to make it easier for customers to contact suppliers, ensure struggling households are supported, and improve overall customer satisfaction.

The regulator has previously raised concerns about customers facing unacceptably long waits for calls to be answered.

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In a speech to the energy sector, Ofgem chief executive Jonathan Brearley warned that global events were putting pressure on gas prices and could lead to higher domestic bills.

"This is why the industry needs to do all it can to ensure good customer services and provide help with managing debt, especially for the most vulnerable," he said.

He said some suppliers had made improvements, but more needed to be done to support vulnerable households.

"Long wait times to speak to someone on the phone; letters not replied to; lack of empathy for people's personal circumstances - this needs to change," he said.

Simon Francis, coordinator of the End Fuel Poverty Coalition, said: "It's not enough for energy firms to just pick up the phone to customers struggling with their bills. With soaring energy debt levels, people need to have their concerns dealt with efficiently and in a sympathetic manner."

Earlier this month, a group of 14 suppliers signed up to a commitment to go beyond current licensing conditions to help households struggling with energy bill debt this winter.