In a village on the flood plains of central Bangladesh, an older woman in a yellow sari huddles outside a hut on stilts. The bare interior contains a cooking pot, a board covered with a mat and a rack holding a few neatly folded saris.

Mumtaz, 62, lives alone and seems resigned to the fact that when the flood water, which laps around the palm trunks a few metres away, reaches her hut, she will move to the local cyclone shelter.

She survives on her widow's pension of 220 taka, or £1.80 a month. "It's enough to buy rice," she says. "I was thankful when I found out I was eligible."

In northern India, Shantabai, 65, sits cross-legged amid a throng of chattering over-60s, the men in loincloths, the women in brightly coloured saris. She is attending her local older people's association, one of an increasing number in India and Bangladesh demanding pensions from the government.

India and Bangladesh both offer means-tested, non-contributory pension schemes for poor older people, but low literacy levels, geographical remoteness, lack of information and confusing bureaucracy mean the majority of such people do not know they are eligible.

When I ask one 72-year-old if she knows she has a right to a pension, she shakes her head, puzzled. "What is a right?"

After the association meeting, Shantabai leads me through searing sunshine to her hut, past cows being milked and women raising water from the well.

Crouched in the darkness is her husband, who has asthma from working with cement and wheezes painfully through his skeletal chest. When I ask why their children don't look after them, Shantabai's eyes fill with tears. "They say we mean nothing to them."

Below the breadline

Shantabai and Mumtaz are growing old in countries where traditional family values are deteriorating. Children are migrating to cities and older people are left to fend for themselves. For them and many others, older people's associations offer a brighter future.

Local association members visited Mumtaz and helped her apply for her pension, and Shantabai and her husband now receive pensions amounting to 425 rupees, or £5.10, a month. It isn't much, Shantabai admits. "Nine rupees a day [her share of the pension] doesn't buy anything nowadays. A cup of tea is three-and-a-half rupees, and wheat is 12 rupees a kilo."

HelpAge International, part-funded by the Department for International Development, has helped older people in over a thousand villages in India and Bangladesh set up such associations, after informing them of their right to a pension.

Vridha mitras, or "older people's helpers", act as go-betweens with local officials and help older people who can't read or write understand complicated application forms requiring proof of poverty.

"The entitlement is there," explains Syed Shahab, project coordinator of HelpAge India. "Older people just don't know who to talk to, and the forms ask complicated questions of people who are unable to read or write.

"They're asked if they own land, without consideration of whether it can be cultivated or whether they're fit enough to tend it. Similarly, an older person can't get a pension if he or she has an adult son. Government assessors simply tick 'yes' without asking whether the son looks after his mother or father socially and financially.

"It's ridiculous. Hundreds of needy older people miss out. That's why we knock on doors to find the truth."

Syed reels off facts. By 2050, the world's over-60 population will reach two billion, outnumbering children for the first time in history. India and Bangladesh have the second- and third-largest populations of poor older people in the world, yet both spend less than 0.5% of their GDP on social pensions, benefiting less than 20% of over-60s.

This is lower than poorer countries like Mauritius, which spends 2% of its GDP on a universal, non means-tested pension scheme benefiting 100% of people over 60.

"The pension systems of India and Bangladesh are failing people," says Anna Pearson, HelpAge International's senior social protection officer. "Schemes aimed at the destitute are so complex that they rarely reach their target.

"They also overlook older people who haven't had formal jobs or contributory pension schemes, but who are extremely poor by international standards. Both countries need universal schemes covering all older people."

Fight for your right

Older people's welfare is an urgent problem, but not a glamorous one. The Indian journalists I meet seem bored by the issue, more interested in the free snacks at Help Age's press conference than gathering information.

"In Bangladesh it's the same," sighs Haseeb Khan, director of HelpAge's Bangladesh partner Resource Integration Centre. "Newspapers don't cover older people's issues. Journalists think older people are going to die soon, so why bother?"

Yet older people are defying stereotypes. "We don't hesitate to make demands of the government, because we're a group," says Abdur Rouf, 75, member of a district association in Pubail, Bangladesh. "If all the older people get together and campaign for pensions, we can't be ignored. We're making a human chain across the country. We're thinking nationally."

"We even persuaded the chief district administrator to give us cards so that we receive free healthcare," adds Xavier Purification, 72, a member of the same committee. "I feel young again, because I'm no longer helpless."

In India, Syed tells stories of older people confronting corrupt officials. "Some recorded a local official demanding a bribe in return for distributing the pension money. They showed him the tape and he released the money, but they kept the tape in case he did it again."

"The associations have given older people new hope, physically and emotionally," says Khan. "They are demanding more and they're right. If the Bangladesh government spent less than 1% of its entire development fund on social pensions, the monthly pension amount would double. The allowance needs to be minimum 500 taka (£4.12), and the government can afford this."

Older people in India and Bangladesh do not yet have a secure future. "We've helped thousands access pensions," says HelpAge's Social Protection Policy Advisor Anna Pearson, "but there are still many who need help. The demographic of ageing people is rising all the time, so what are India and Bangladesh going to do about it?"

On October 1, the UN's International Day of Older People, delegations of older people met parliament members in Dhaka and Delhi to demand pensions for everyone over 70 and an increase to the existing monthly pension amount. It remains to be seen whether they will live long enough to see their efforts pay off.