More than 250,000 rural pensioners are failing to claim pension credit, an independent watchdog has warned.
The report says pensioners are missing out on vital financial help
The Commission for Rural Communities says 42% of eligible pensioners do not receive the benefit, compared with 35% in urban areas.
Take-up for pensioners living in more isolated areas is even worse, with fewer than 50% getting the financial help to which they are entitled.
The government says it is making "every effort" to improve take-up.
Pension credit is a means-tested benefit which guarantees people aged 60 or above a weekly income of £119.05 for a single person and £181.70 for couples.
Pensioners aged 65 or above with extra income may also qualify for extra help on top.
Pension credit is currently paid to about 2.73 million people. However, almost a third of the people who are eligible for the benefit do not claim.
That figure that has remained fairly constant since the benefit was introduced in 2003, leading to fears the government may miss its target to reach 3.2 million households by 2008.
Research from the Commission for Rural Communities has now shown that take-up is significantly worse in rural areas than in urban centres, especially in more remote parts of the country.
It estimates more than 250,000 rural pensioners are missing out.
"The situation... is extremely concerning, especially as the rural population is ageing faster than the urban population," said the commission's director of practice Graham Russell.
He says one cause may be that pensioners in rural areas are isolated from sources of information and advice.
In addition, they could be more independent, or more anxious about the potential stigma of receiving a means-tested benefit.
"Pensioners are entitled to claim this allowance; it is imperative that no one who is in genuine need misses out, no matter where they live," he added.
Help the Aged described the findings as "very worrying".
"It is vital that the government provides funding for face-to-face benefits advice projects in rural areas to increase take-up," said Anna Pearson from Help the Aged.
"In addition, urgent attention needs to be given to introducing a system of paying benefits to people automatically," she added.
The Department for Work and Pensions (DWP) said it was making "every effort" to ensure that pensioners receive the correct benefits.
HOW TO CLAIM PENSION CREDIT
Online at www.thepensionservice.gov.uk
By calling 0800 99 1234
Textphone 0800 169 0133
A DWP spokesman said its local service would visit around 13,000 pensioners who may be entitled to extra help in 2007/8.
Appointments take place in the pensioner's home or at one of 787 information points across the UK, around half of which are in rural areas.
The government also stressed it is possible to claim pension credit over the phone, without any form-filling. Pensioners can also apply for housing benefit and council tax benefit at the same time.