The NHS should offer checks for dementia when people reach 75, a leading health charity says.
The Alzheimer's Society says fewer than half of those with the condition get a diagnosis, so many miss out on the care and support they need.
The UK National Screening Committee, which advises the NHS, has said tests and treatments need to improve first.
And the British Medical Association says carrying out the checks would mean there is less time for other services.
About 750,000 people in the UK have dementia - and with the numbers projected to rise to more than a million by 2021 the Alzheimer's Society says it is essential to identify those who need help.
'The only way'
Professor Clive Ballard, the charity's director of research, says getting a diagnosis is fundamental to ensuring the right treatment, support and care.
"Really the only way we're going to improve identification is through effective screening, and probably the right time to do that screening is over the age of 75 once dementia starts to become more common."
He is proposing that people be offered a cognitive test at the GP surgery, with questions on time, date, place, memory and understanding. This would be backed up by an interview with a relative or carer.
Where dementia is suspected patients would be referred to a specialist for a full clinical assessment. If they were then diagnosed with dementia, there may be drug treatment and changes in lifestyle that could help delay deterioration, and would allow an opportunity to plan ahead, he argues.
Prefer not to know
Dr Shabana Chaudhari, a GP in south London, says she already carries out a cognitive test if she has concerns. However she says screening for dementia presents particular problems.
"You would have to explain why you were doing the test. But what you would also have to do is ask, if there was any impairment, do they want to know, because some people don't want to know. And if there is anything, do they want their family and friends to know about it as well."
Dr Laurence Buckman, from the British Medical Association, says there is value in the idea of screening for dementia, and that many GPs would be happy to carry it out. But he says many would struggle to find the time.
"It takes an hour to do an assessment, during which time five other patients could have been seen. In the current economic climate, when the NHS is being asked to make huge efficiency savings and there are many equally valid competing demands, patients and the public need to have a debate over which services should be prioritised."
The idea of screening for dementia was examined in 2009 by the UK National Screening Committee, which advises ministers and the NHS.
The committee's programme director, Dr Anne Mackie, says the initial checks are not yet sufficiently reliable. She is worried that while dementia may be missed in some patients, others may be told incorrectly that they are at higher risk, causing needless distress.
She suggests that for the time being the money for screening "would be better spent on research, finding better treatments, or providing support for carers".