Energy regulator Ofgem has instructed gas and electricity companies to ensure their poorest customers are on the cheapest deals they offer.

Currently the cheapest offers are often reserved for internet customers, ruling out those customers who cannot afford or gain access to the internet.

"Some consumers may still be able to get a better deal by switching to another supplier, particularly if they are also able to change payment method," said Ofgem.

"But for customers who are unlikely or unable to switch and are eligible for a social tariff, this ruling means they can be assured they will be on their supplier's best deal," it said.

The ruling was backed by the Energy Retailers' Association and Energywatch, but both warned the move would not in itself halt fuel poverty, defined as when 10% of household income goes on energy bills.