More than two in five low-income over-65s in St Helens are missing out on their Pension Credits, new analysis shows.
Anti-poverty charity Turn2Us said pensioners were falling foul of "digital exclusion", and called on the Government to make the benefit more accessible to people with low computer literacy.
The charity estimates 5,047 people in St Helens were not claiming Pension Credit – a means-tested benefit for low-income pensioners – in February this year, despite being entitled to it.
That's 42% of eligible claimants in the area .
Pension Credit tops up the income of over-65s to a minimum level – £167.25 per week for single people and £255.25 for couples.
Turn2Us estimates that £11.2 million went unclaimed in St Helens over just one year.
David Samson, welfare benefits specialist at the charity, said: "Pension Credit is not a luxury, it makes a significant difference in weekly income.
"We work with people every day who are struggling financially, and we know that older people are often the least equipped to get the right support at the right time.
"We believe that a lack of information, along with digital exclusion amongst this age group, is a major reason for the lack of claiming."
The charity reported providing advice and support to over 90,000 over-65s last year, a 61% increase on the year before.
Charity Age UK raised concerns that the current application system is forcing older people to "jump through hoops to get the money that is due to them".
Director Caroline Abrahams said: "Successive governments have not tried terribly hard to increase take-up of Pension Credit.
"The treasury pockets billions that ought to be supporting older people on low incomes to live decently.
"At the very least the application process needs to be made easier, and more needs to be done to raise awareness that Pension Credit exists.
"However, ideally older people would not have to ask for extra money to bring up their incomes to a decent level at all.
"It would either come to them automatically, or their State Pension would provide them with an adequate amount in the first place."
Across Britain, more than 1.3 million low-income pensioners are not claiming the benefits they are entitled to.
The DWP said it encourages people to check if they qualify for Pension Credit, and distributes information via leaflets and Jobcentre staff, as well as online.
A spokesperson said: "Pension Credit is an important protection for some of the most vulnerable people, and we want everyone to claim what they are entitled to.
"Anyone who claims their State Pension receives a letter encouraging them to call us to discuss their Pension Credit entitlement."