Up to a million poor pensioners will miss out on vital help with winter fuel bills as freezing weather grips Britain this week.

Ministers have been branded “cruel” after refusing to extend the deadline for pension credit applications.

With temperatures expected to fall below zero this week, charity bosses warned the harsh decision could cost lives.

Many elderly folk are struggling to complete the daunting 24-page form – which contains 243 questions – in time for the cut-off.

It means they will be unable to claim either pension credit or the winter fuel allowance of up to £300 this year.

Ministers have admitted that officials may take longer than the 10-day target to process applications that arrive in time.

Former pensions minister Baroness Altmann said the policy was “extremely cruel, poorly conceived and actually dangerous.”

She told the Sunday Express: “The Department for Work and Pensions is struggling to deal with the new pension credit applications it has already received, let alone any more that will come along.

“Those eligible for help may still not receive anything this winter unless some changes are made, which so far there is no sign of.

“I truly fear for the lives of some of these frail, elderly people as the weather gets cold.”

Weather experts have warned winter will begin to bite this week, with sub-zero temperatures likely in parts of northern England and Scotland.

Joanna Elson, chief executive at campaigning charity Independent Age, warned: “There is simply not enough time to get pension credit to everyone who is eligible.

“The latest figures show that almost one million eligible older people could be missing out on the entitlement, meaning they will now lose the winter fuel payment despite living on a low income.”

She said: “We have heard harrowing accounts of people planning to visit public places to stay warm, live in just one room and reduce the amount of food they eat. People in modern Britain shouldn’t have to live like this.

“The December deadline is fast approaching and too many older people in financial hardship risk being left out in the cold this winter.”

The crisis is a result of the Government’s decision to means-test winter fuel payments, which were previously available to all pensioners.

The cash is now offered only to those receiving other benefits such as pension credit, but many fail to claim this despite being eligible.

Temperatures are expected to fall to freezing this week with the Met Office predicting likely nighttime temperatures of zero in the north of England and minus 1 in Edinburgh, while in the Scottish highlands they are set to fall to minus 7.

Calls for the deadline to be extended beyond December 21 have come from across the political spectrum.

Labour MP Rachael Maskell said: “I am deeply concerned about older people being cold this winter and as a result falling unwell or even dying.

“Now the nights are getting colder it is vital that fuel-poor pensioners have more time to claim their winter fuel payments and more support to stay warm and well.”

Liberal Democrats are also demanding an extension but Work and Pensions Secretary Liz Kendall has told MPs that pensioners who fail to meet the deadline will not receive the money.

Eamonn Donaghy, spokesperson for Later Life Ambitions, which represents more than 250,000 pensioners, said: “The reality of this Government’s decision to axe winter fuel payments for millions of pensioners is really coming home to roost as temperatures start to freeze.

“It would be an outrage if any pensioner is caused unnecessary worry or suffering this winter due to overbearing bureaucracy and for want of basic compassion.”

The DWP has a target of processing 85% of new pension credit claims within 10 days but Ms Kendall admitted this may not be possible, despite deploying more than 500 additional staff to deal with applications.

In a letter to the Social Security Advisory Committee she said: “The Department has a strong desire to meet its published timeliness standard of processing claims but that will depend on the complexity of claims and overall level of claims intake.”

The committee is the official body created to provide impartial advice to the DWP but the minister has rejected its call for winter fuel allowance to be paid automatically to 120,000 pensioner households receiving housing benefit.

She also admitted her department does not know how many pensioners will be plunged into poverty as a result of means-testing and the committee wrote to her calling for a full assessment of the “potential poverty impact.”

She replied: “There is general uncertainty in the estimates of those who are eligible for pension credit but not in receipt of it, given the complexity of estimation.”

A DWP spokesperson said: “We want to ensure all pensioners get the support they’re entitled to, which is why we are deploying over 500 extra staff to process the expected increase in claims.

“Our pension credit campaign has also been successful in boosting applications by 152%.

“Successful claims for pension credit can be backdated by three months, so all eligible claims made by December 21 would also receive a winter fuel payment as well as arrears of pension credit.

“We continue to urge anyone who thinks they may be entitled to pension credit to check now.”

The Northern Ireland government last week announced it would provide £17million of funding to offset Labour’s winter fuel cuts, providing its pensioners with around £80 each.