Three hundred thousand pensioners have fallen into poverty over the last year, the government has revealed.
The data means 822 pensioners become poverty-stricken every day.
Mervyn Kohler, special adviser for Help the Aged, said: "When older people live on a fixed income it is virtually impossible for them to pull themselves out of poverty.
"Pensioners often have to cut back on essential household items, just to survive."
The group is accusing the government of sitting on £5 billion of unclaimed benefits for old people every year.
"While this figure may make the chancellor rub his hands together with glee, this daylight robbery of older people must not be allowed to continue," Mr Kohler continued.
"It is up to the government to ensure older people get the benefits they're entitled to and these should be paid automatically."
The news comes as annual child poverty figures show a second consecutive rise, meaning the number of children living in poverty has increased by 100,000.
The number of children living in poverty is now 9 million.
Commenting on the figures, Kate Green, chief executive of the child poverty action group, said: "Ministers cannot take a holiday from their promise to end child poverty, or this is what happens.
"Every year progress must be planned, invested in and achieved. And every year we must act to end the inequality that is blighting Britain and turning us into a divided nation."
Martin Narey, chief executive of Barnardo's, said: "This is not the time to lose heart. Taking account of measures already in the pipeline, the government is still more than half way toward the astonishing target of halving by 2010 the number of children in poverty which they inherited from the Conservatives.
"More than three million children in this, the fifth richest country in the world, are living in poverty - a fact which shames us all. So, this is not the time for warm words from the chancellor about hoping to meet the target. He should announce, now, exactly how it will be done."
Liberal Democrat work and pensions spokesperson Jenny Willott said: "It is impossible to understand why, as one of the wealthiest countries in the world, Britain should have one in five of its children living in poverty.
"Unfortunately, options are limited thanks to the 10p tax debacle which has left Gordon Brown with little in the bank to offer the millions of overstretched families struggling to make ends meet."