A report by the charity refers to research showing that people aged 50-plus are twice as likely to vote as younger people, and are among the most likely to switch their party allegiance.
The charity has also distributed its election manifesto at all three party conferences. Isn't it time politicians stopped just kissing babies?
recommends that the next government should increase state pensions; combat ageism at work, in hospitals and in consumer services; and build effective public services capable of supporting an ageing population.
The charity issued a stark warning that any party that doesn't add manifesto commitments for older people is likely to face a spell on the sidelines.
Age Concern is talking tough in a bid to ensure that the Government and its rival parties act on its campaign wish-list. "Pensioners' votes really could determine the outcome of the next election, and many of them are disillusioned," said Michelle Mitchell, head of public affairs at Age Concern.
"We're putting out a really hard message because that is the reality," said Mitchell. "There are 17 million baby-boomers heading towards retirement.
We are saying to them: make your voice heard because your votes are crucial." Age Concern sent copies of its election manifesto to its regional offices to display last month.
The charity's report has categorised voters between the ages of 45 and 69 in six groups. It states that "healthy wealthies" and "measured traditionalists" are likely to vote Conservative, while those categorised as "life lovers", "home comforts", "good-time grafters", and "worn-out worriers" would mostly vote Labour.