More must be done to ensure older people receive billions of pounds in unclaimed benefits, according to the charity Age Concern.
Not all pensioners are claiming their full amount of benefits
It says pensioners could dramatically improve their lives by claiming full entitlements estimated at £4.2bn.
It is launching a campaign, called Your Rights, aimed at helping older people claim an extra £100m by April 2008.
In response, the government said that it has made "tackling pensioner poverty its first priority".
Gordon Lishman, Director General of Age Concern, said: "Millions of older people across the UK are missing out on money that is rightfully theirs and could make a huge difference to their quality of life.
"There is nothing to lose and everything to gain by making a claim.
"Claiming Council Tax Benefit alone could cut bills by an average of £580 a year and claiming Housing Benefit could mean paying less or no rent at all."
Almost 50% of those who could claim benefit - up to 2.2 million pensioner households - are said to be missing out.
The charity warns that some of the poorest older people are unaware of what they are entitled to, have concerns over the complexity of the process or too embarrassed too claim.
A spokesman for the Department for Work and Pensions said: "Because the government has made tackling pensioner poverty its first priority, initiatives such as Pension Credit have helped to lift more than two million pensioners out of absolute poverty, and a million out of relative poverty.
"Today, no pensioner should be living on less than £119 per week - compared to £69 per week 10 years ago.
"Last year we contacted 278,500 pensioners who we believed may have been entitled and, as a direct result, we are now paying an additional £650,000 a week in council tax benefit to pensioners compared to the same time last year."