Specialists from the UK and Australia, writing in the BMJ, said policies in the UK and US to increase dementia detection rates will diagnose two-thirds of people aged over 80 with Alzheimer's disease. Up to 23% of older people could be mislabelled with the disease.
They criticised this 'war on dementia', saying it is not backed up by evidence and does not consider the risks and harms of diagnosis.
But a leading dementia charity said the UK could not afford to ignore the condition.
The new dementia directed enhanced service pays GPs to assess 'at-risk' patients, such as those over 60 with diabetes or cardiovascular disease, for signs of cognitive impairment. The government has also pledged to increase the number of memory clinics.
But uncertainty remains over the accuracy of tools used to diagnose dementia, the experts said. Drugs are only able to slow disease progression rather than halt it, they added, and unnecessary treatment raises the risk of adverse effects.
They concluded: 'Current policy is rolling out untested and uncontrolled experiments in the frailest people in society without a rigorous evaluation of benefits and harms.'
RCGP chairwoman Professor Clare Gerada said the report would be welcomed by 'thousands of GPs concerned about screening for dementia'. She said it could create problems by generating false positives that worry patients and families, and increase unnecessary referrals.
She called for 'more resources and far greater access to services such as memory clinics' and said it could be difficult to diagnose dementia, but often memory lapses were simply due to old age.
'What GPs and patients need are greater resources in the community to enable us to support people and help them live independent lives,' said Professor Gerada.
Jeremy Hughes, chief executive of the Alzheimer's Society, said: 'It's astounding to hear talk of an "unwanted war" on dementia when in fact we need nothing less than an all-out fightback. We should be backing doctors who are helping ensure people with dementia are diagnosed.'
He said discussion of screening was 'irrelevant' as this is not what has been suggested by policies. 'By 2021, a million people will have dementia. We can't bury our heads in the sand.'