-> Yorkshire grandfather's fear of 'miserable existence' if TV licence lostThe benefit will be restricted to those on pension credit from June next year, with the BBC saying it cannot afford to take on the financial burden from the Government.
The broadcaster recently told MPs that over-75s will have home visits from BBC "outreach" teams.
Age UK said that many pensioners, including those who find it difficult to dress, bathe and get out of bed, will struggle with the procedure of paying or even confirming that they are entitled to a free TV licence.
-> Time to put OAPs before celebrity presenters in BBC licence fee and pay row – Jayne DowleCharity director Caroline Abrahams said: "The idea that more than a million over-75s who are coping with serious health and care challenges will be able to comply with a new TV licence process, having never done so before, is cloud cuckoo land.
"However straightforward the process, it will still defeat many of them, unless they have friends and family who can help, and unfortunately a lot don't."
Age UK said that more than a quarter (29 per cent) of over-75s in the UK have difficulty with at least one activity of daily living.
The BBC's director of policy Clare Sumner told a Commons select committee earlier this month that the home visits would be done "as sympathetically as possible".
"We are actually recruiting a specific group of people who will pay support visits to this group with the intention of helping them understand what the system is and how to apply," she said.
"Now that will be a different cohort of people to I think what's called 'enquiry officers' who are the ones who kind of enforce the licence fee."
-> Do all over-75s need a free TV licence? - Yorkshire Post lettersMs Abrahams warned there "will be difficulties" whether or not an older person is entitled to a free TV licence.
She said the process was "simple enough" for people with "home computers and scanners, but most over-75s are not online...
"And for anyone who finds it difficult to get around, or who is housebound or indeed bedbound, it will be a lot more challenging still."
She said: "The BBC's setting up of 'visiting teams' may be designed to be helpful but that's not how most older people we have talked to have reacted to the idea.
"This is what happens when a government tries to outsource social policy and delivery to a body like the BBC with no experience or expertise in this field - nor with any in-depth understanding of over-75s and their lives. A slow motion car crash is a foregone conclusion if the BBC is allowed to carry on with its means-testing plan."
She called on new Prime Minister Boris Johnson to "abide by the last Conservative manifesto and continue to fund a free licence for our over-75s."
Age UK said that 20 per cent of over-75s have difficulty dressing, and 16 per cent bathing or showering.
Around nine per cent struggle to get in and out of bed and seven per cent have difficulty walking across a room.
Around 672,000 are living with dementia and a further 662,000 with "severe frailty", it said.
The free TV licence was introduced in 2000, but the BBC agreed to take on the cost as part of the charter agreement hammered out in 2015.
Dame Helen Mirren, Dame Vera Lynn, Sir Lenny Henry and Len Goodman have all called for the universal entitlement to be restored.
The BBC said it had written to 25 organisations, including Dementia UK, and is working with them to help support people and raise the visibility of Pension Credit.
A BBC spokesman said: "We've reached the fairest decision we can - one that protects the poorest pensioners while ensuring everyone will continue to receive the best programmes and services that the BBC can provide.
"TV Licensing recognises that some people are vulnerable and it's important to provide additional support and reasonable adjustments for these customers.
"We want to work very closely with organisations working with older people to offer as much help as we can and we know that customers may prefer a family member or carer to deal with their TV Licence on their behalf, so we already have mechanisms in place to facilitate this."
The spokesman added: "We recognise that this group may also welcome more personal support, either through a TV Licensing hotline or by a visit.
"From next year, TV Licensing will be providing face to face assistance for older people through an outreach programme delivered by specially trained staff. Their sole purpose is to help people apply for their licence, including a free licence, and raise awareness of Pension Credit. They will not arrive unannounced and will not be involved in enforcement action."