Relatives of care home residents with dementia should be treated as key workers, leading charities say.
In a letter to the health secretary, they write that the care given by family members is "essential" to residents' mental and physical health.
They argue the current limits on visitors have had "damaging consequences".
They want visits to resume safely, with relatives given the same access to care homes and coronavirus testing as staff.
Signed by the bosses of leading charities including Dementia UK and the Alzheimer's Society, the letter calls on the government to "urgently" address what it calls the "hidden catastrophe" happening in care homes.
A spokesman for the Department of Health and Social Care (DHSC) has told the BBC it will be setting out further details "shortly" on how it can "carefully and safely" allow visiting in care homes.
In April, the DHSC said in a document that all "family and friends should be advised not to visit care homes, except next of kin in exceptional situations such as end of life".
The charities say that this "enforced separation" has caused a "deterioration" in residents' mental and physical health, particularly for those living with dementia – who make up more than 70% of the population of care homes.
They argue that family carers remain "essential members of the residents' care and support network", in providing practical services as well as being their "advocates, voice and memory", and "keeping them connected to the world".
They are calling on Health Secretary Matt Hancock to publish detailed guidance on care home visits, and grant certain relatives and friends the same "key worker" status as members of staff – which would allow them the same access to care homes and coronavirus testing.
During the pandemic, there have been 5,404 excess deaths – an increase of 52.2% compared with the five-year average – of people with dementia and Alzheimer's disease in England and Wales, according to the Office for National Statistics (ONS).
'I've only got one mother'
Rosie's mother has severe dementia and lives in a care home.
For months she couldn't visit, but when she did, two weeks ago, Rosie was shocked.
Her mother was "quite slumped over in her wheelchair". It took her a long time to respond.
Rosie could see she'd changed a lot.
Worse still, in the last fortnight her mother has stopped eating, refusing to open her mouth when care home workers try to feed her. Rosie is now worried that she might refuse liquids too, and die.
Rosie is relieved that the health secretary is promising guidance to allow visits – but also concerned that it may limit how these can happen.
Before coronavirus hit, Rosie's mother had visits every day from family or friends.
They would sit with her for at least an hour, talking to her. Rosie would sing Motown songs which her mother loves.
"Her face would light up, she'd try to sing along" she said. Sometimes she brought food, or would take her out of the home. She liked going to the pub.
Now that her mother is so much worse, Rosie would like to be treated in the same way as a paid care worker, to be allowed into the home and sit with her mother.
She would be tested for Covid-19, and wear personal protective equipment (PPE). This is something leading dementia charities are saying must made possible under new guidance.
"I'm her voice, her advocate" Rosie says.
"I should be with her. I've only got one mother. I'm not prepared to let her die without me there".
In the letter, the charities say the "inconsistency" of the visiting guidance across the UK nations is causing "additional confusion and stress" for providers and family members.
In Scotland, care homes that are virus-free for 28 days were able to accept visitors from 3 July.
In Northern Ireland, as of Monday, care homes that are free from the virus can allow one person to visit at a time, with a second person accommodated "where possible".
In Wales, visits have been allowed to care homes and their residents since 1 June, provided they take place outside and 2m social distancing rules and hygiene procedures are followed.
Care England, which represents most of the independent providers, says new guidance in England is essential – and it is "not right to keep people with care and support needs locked down indefinitely".