Cold weather fuel payments to pensioners must be increased as the extreme winter weather continues, Age Concern and Help the Aged have urged.
Eligible pensioners get cold weather payments if the temperature plunges below normal for more than seven consecutive days.
The call comes as Britain braces itself for icy blasts as the freezing weather looks set to continue over the weekend.
The weather is causing major disruption to the weekend's sporting programme.
Five Premier League games have been called off - at Sunderland, Fulham, Hull, Burnley and Liverpool - as well as dozens of other league games.
Horse racing meetings across the country have also been cancelled, with a series of rugby union matches postponed.
As Britain's coldest spell for 30 years continues, the charities fear the existing government support will not be enough to prevent a soaring death rate among older people.
Last winter, 36,700 more people died than would have been expected, nearly 50% more than the previous year's figures.
Andrew Harrop, head of policy at Age Concern and Help the Aged, said: "Many older people will be worried about paying even higher energy bills to heat their homes.
"Cold weather and winter fuel payments have provided welcome extra cash to help lower income households pay their heating costs.
"But these one-off payments haven't kept pace with the steep increase to energy bills over the last few years and are only a sticking plaster to the entrenched problem of fuel poverty."
Currently, the over 60s get £250 in one-off winter fuel payments, while the over 80s get £400. Older people who receive pension credit also get a cold weather payment if the temperature plunges below normal for more than seven consecutive days.
Energy minister David Kidney said: "We specially increased the cold weather payment last year from £8.50 a week to £25 a week which is a substantial increase.
"We kept it at that high level this year precisely for this kind of situation and it will be paid every week that the weather is particularly cold to all the people who are entitled to it."
Meanwhile, the government has stepped in to conserve road-gritting stocks due to dwindling salt supplies.
The Transport Secretary, Lord Adonis, said local authorities had agreed to cut salt use by 25%.
The Conservatives have said that the government's move is "an admission of utter failure" and plans should have been made earlier.
As temperatures remained at sub-zero levels, at least 24 people are believed to have died since before Christmas in weather-related incidents.
The latest are two brothers who died in hospital in Leicester after falling through the ice at Watermead Country Park.
Forecasters say it will feel colder overnight because of an "increased wind chill" coming from Germany and Poland.
Up to 20cm (7.8in) of snow is forecast for parts of South Yorkshire and to the south of London - from Essex to Brighton.
Forecasters have warned that the freezing conditions could last at least another week.
Prime Minister Gordon Brown spoke to several ministers and agencies about the severe weather during a ministerial meeting at the Cabinet Office and said the government was doing it all it could.
Energy Secretary Ed Miliband said there was no need to worry about energy supplies and that the situation was being closely monitored.
BBC weather forecaster Rob McElwee said snowfall of up to 3cm (1.2in) was expected elsewhere in England late Saturday and on Sunday but Scotland and Wales were not likely to see record-breaking temperatures overnight.
He said: "The wind is picking up and there will be an increased wind chill. For humans that is the big factor that will make it seem colder."
Friday saw the UK's coldest day so far when the mercury plunged to -22.3C (-8.1F) in the Highland village of Altnaharra.
The government has insisted schools should stay open "wherever reasonably practicable" during severe weather although more than 8,000 schools remained closed on Friday.
However there are fears that thousands of students in England, Wales and Northern Ireland may have to wait another five months to take exam modules because of the problems caused by the weather.
The Royal Society for the Protection of Birds has warned the cold weather threatens to be the greatest wildlife disaster of the new millennium.
It says that the freeze could be the single biggest killer of birds since the Arctic snap of the early 1960s and has asked the public to help feed them.
Updates can be found at BBC Travel News
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