The number of pensioners claiming council tax benefit has fallen, official figures show.
Pensioners failed to claim £770m
About four in 10 eligible pensioners failed to claim the benefit in 2001/02, the government said.
Many pensioners say the benefit, which can reduce their council tax bills, is complex and some find it demeaning.
Pensioners are conducting a high-profile campaign against big rises in council tax, some of whom are risking jail if they fail to pay up.
The maximum number of pensioners who could have claimed Council Tax Benefit (CTB) between 2000/01 and 2001/02 may have fallen by as much as from 68% to 63%, the figures show.
In 2001/02 this means as many as 1.76m pensioners failed to claim up to £770m of help from the government.
The government has acknowledged that uptake needs to be improved.
PENSIONERS CLAIMING COUNCIL TAX BENEFIT
2000/01: Up to 1.43m pensioners not claiming. Up to £580m unclaimed
2001/02: Up to 1.76m not claiming. Up to £770m unclaimed
It recently said it would start an information and advertising campaign aimed at promoting take-up shortly.
Steve Webb, Liberal Democrats Shadow Work and Pensions Secretary, said it was a "disgrace" that so many pensioners were missing out on help.
"Pensioners face a Council Tax double-whammy. First they are hit by the unfair tax. Then they are faced with a complex benefit that even Einstein couldn't understand," he said.