West Midlands GPs believe patients with dementia are being failed by the authorities - with the burden for care falling on family members.
A poll by the Alzheimer's Society said most doctors in the region believed adult social services were not giving enough support.
The study of GPs found 67 per cent thought their patients with dementia were not receiving enough support, with 77 per cent saying dementia patients had to rely on family members, friends and neighbours - rather than the health service and local councils.
The West Midlands currently has 73,000 people with dementia.
Jeremy Hughes, chief executive of the Alzheimer's Society, said: "Our survey gives a stark view from the doctor's surgery of people with dementia left struggling in the aftermath of a diagnosis.
"GPs report an endemic and deeply worrying lack of support available from health and social services, with relatives left to pick up the pieces alone.
"People can need a lot of help to live well with dementia. Families and friends are a vital source of support but they mustn't be relied on to do everything.
"With the number of people with dementia expected to grow to one million by 2021, there is no time to waste."
David Ash, regional operations manager for the West Midlands, said: "These recent findings go to show just how important it is for health and social care services to be working together to support people with dementia and their families.
"We are pleased to be involved in providing services in the West Midlands and are already seeing an improvement in diagnosis rates through improved GP awareness.
"A diagnosis opens the door on accessing support so should not be underestimated as a part of this package of care.
"We need to see this support for vital services rolled out across the country, to allow GPs to have greater confidence in diagnosing and referring patients."
The Alzheimer's Society is calling on the Government to set out how the Prime Minister's 'Challenge on Dementia 2020' will be actioned.
It is urging statutory and voluntary services to work together and create a single point of contact to help those affected by dementia navigate the health and social care system.
Mr Ash added: "A future where people with dementia across the UK all have access to the same package of care, including a dementia adviser, would help alleviate the burden that families face when receiving a diagnosis of dementia.
"These trained specialists can provide someone with a named contact throughout their journey with dementia."
The survey also suggests patients' lack of access to services may be undermining a national drive to improve rates of dementia diagnosis, with more than a quarter of GPs admitting they would be less likely to refer people with suspected dementia for diagnosis if support services are not in place.
A Department of Health spokesman said: "Dementia training has already been given to 600,000 NHS and social care staff and our diagnosis rates are now among the highest in the world.
"After a diagnosis, we are already expanding access to named clinicians and dementia advisers to help patients and their families and giving the option of personal budgets - and we want to see these things being offered across the NHS.
"The Prime Minister has set out a further challenge for all NHS and social care staff to be trained in order to provide meaningful care and support for people with dementia, their carers and their families."