The energy regulator Ofgem has announced it will extend its price cap to one million more vulnerable households this winter.
Ofgem said the extension of its prepayment safeguard tariff will save the households around £120 a year on average. A wider cap for all consumers on standard variable tariffs will only be possible once legislation is in place, according to the regulator.
It has also urged suppliers to help move customers onto better value deals.
The regulator said it will work on extending price protection to at least 2m more vulnerable households for winter next year, once the timing of the government's price cap is put in place.
The Prime Minister sent shares in energy firms falling when she pledged to cap energy prices during her Conservative party conference speech, saying she would bring an end "to rip off energy prices once and for all".
Ofgem said it will work with the government to ensure that those on standard variable and other default tariffs receive price protection as soon as possible "if legislation is in place". It will consult on the design of the price cap for default deals while the government's draft bill progresses through parliament.
For now, the regulator said suppliers must ramp up their efforts to get more of their customers on default tariffs onto better value deals.
Today, it is introducing new rules allowing suppliers to roll customers onto another fixed deal if they're coming to the end of their contract, as opposed to a poor value standard variable tariff.
Dermot Nolan, chief executive of Ofgem, said:
Ofgem shares the government’s concern that the energy market is not working for all consumers and is determined to reduce the detriment suffered by those overpaying for their energy, particularly those who are vulnerable.
He added: "The introduction of further price protections will give time for Ofgem’s reforms to work and for smart meters to be rolled out across the country as we move towards a smarter, fairer, more competitive market."