Ofgem has announced a cap on the electricity and gas bills of one million vulnerable households this winter.
However, campaigners argued this was a “dereliction of duty” as all energy customers should be protected from rip-off charges.
Fuel Poverty Action (FPA), which campaigns against rip-off energy prices, insisted that without government action more people will die because they cannot afford to heat their homes.
It called for all 17 million energy customers in Britain to be protected from profiteering energy suppliers.
In April Ofgem announced a limited price cap on energy for 2.6 million customers who use pre-payment meters, the most expensive way of buying energy.
The policy was condemned as “Marxist” by the government when it was proposed by the then Labour leader Ed Miliband.
Now Ofgem plans to extend the price cap to another one million customers.
FPA's Ruth London said: “There can be no excuse for Ofgem’s failure to introduce a price cap covering all the 17 million customers now being ripped off by high default energy prices.
“Even the government has admitted a cap is needed as the market ‘is not working’ and that energy prices are a ‘rip-off'."
To make matters worse Ofgem has said that the government's proposed energy price cap, announced last week, is unlikely to take effect before winter when vulnerable and elderly residents will need it most.
Ms London said the limited price cap came “at the expense of people who, this winter, will be shivering in their homes, spiralling into debt, and going without food.
“A further delay will undoubtedly lead to more deaths."
Shadow energy secretary Rebecca Long-Bailey said: "The government needs to hurry up and get on with it if customers are to feel the benefit this winter.
"It is now mid-October and we are yet to have sight of the legislation.”
In its election manifesto Labour pledged to take energy provision back into public ownership if elected.
This summer the profits of the “big six” energy companies hit their highest-ever levels, according to Ofgem, while an average of 25,000 people die every year from the cold.