Funding for research into dementia is to be doubled to £66m by 2015 to try to make the UK a world leader in the field, David Cameron will announce.
The prime minister is expected to say in a speech that the level of diagnosis, understanding and awareness of dementia is "shockingly low".
Dementia is thought to affect around 800,000 people in the UK, with the cost to society estimated at £23bn.
In the next decade, the number with the disease is expected to top one million.
Mr Cameron will set out plans to step up research into cures and treatments and to ensure that the health and social care systems are equipped to deal with the problem.
Mr Cameron will say: "One of the greatest challenges of our time is what I'd call the quiet crisis, one that steals lives and tears at the hearts of families, but that relative to its impact is hardly acknowledged.
"Dementia is simply a terrible disease. And it is a scandal that we as a country haven't kept pace with it.
The level of diagnosis, understanding and awareness of dementia is shockingly low. It is as though we've been in collective denial."
The prime minister will say that the costs associated with the disease are already higher than those for cancer, heart disease or stroke.
"So my argument today is that we've got to treat this like the national crisis it is. We need an all-out fightback against this disease, one that cuts across society.
"We did it with cancer in the 70s. With HIV in the 80s and 90s. We fought the stigma, stepped up to the challenge and made massive in-roads into fighting these killers.
"Now we've got to do the same with dementia. This is a personal priority of mine, and it's got an ambition to match.
"That ambition - nothing less than for Britain to be a world leader in dementia research and care."
Overall funding for dementia research in 2010 totalled £26.6m. Under the plan for 2015, it will be £66m.
Care Services Minister Paul Burstow told BBC Breakfast that in addition to the money for research, an extra £54m would be given to hospitals to help the earlier diagnosis of dementia.
'Role to play'
Jeremy Hughes, chief executive of the Alzheimer's Society, said the announcement would mark an "unprecedented step" towards making the UK a world leader in tackling dementia.
"Doubling funding for research, tackling diagnosis and calling for a radical shift in the way we talk, think and act on dementia will help to transform lives," he said.
"There are currently 800,000 people with dementia, yet too many are not able to live well with the condition.
"The PM is leading the way, but from Plymouth to Preston, from the boardroom to bus drivers, we all have a role to play."
David Rogers, chairman of the Local Government Association's community wellbeing board, said: "We now need politicians to transcend political point-scoring and wake up to the ticking demographic time bomb this country is facing.
"There needs to be urgent action to ensure the way we offer support to older people is fairer, simpler and fit for purpose in order to truly meet the needs of the most vulnerable members of our society."