The prime minister David Cameron has described dementia as a 'quiet crisis' that 'steals lives and tears at the heart of families', as he launched 'a national challenge on dementia'.

If anyone was in any doubt as to the scale of the challenge we face in caring for people with dementia, then prime minister David Cameron summed it up by comparing the condition to cancer and HIV.

In a speech yesterday launching extra funding for research into dementia, Mr Cameron declared that tackling the 'national crisis' posed by the disease is one of his personal priorities.

He said it is a 'scandal'' that the UK has not done more to address dementia, which is thought to affect 670,000 people although about 400,000 have not been diagnosed and do not know they have it. Over the next 10 years, the number with the disease is expected to rise to one million.

Mr Cameron 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.

Overall funding for dementia research is to reach �66m by 2015, from �26.6m in 2010 and hospitals will be given an extra �54m to assist the diagnosis of the disease.

Mr Cameron said: '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 said that the costs associated with the disease, estimated at �23bn, are already higher than those for cancer, heart disease or stroke.

He said: 'So my argument today is that we've got to treat this like the national crisis it is. We need an all-out fight-back 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.''

The scale of the challenge has been apparent for some time to health and social care providers in Norfolk and Suffolk.

Both counties are expected to have a greater than average increase in their elderly population in the next few years, which means a greater than average number of people with dementia.

Last year the Norfolk and Suffolk Dementia Alliance was launched in a bid to co-ordinate the joint efforts of councils, health providers, care homes, as well as a host of other independent and voluntary organisations.

It has already drawn up a guide which identifies the knowledge and skills that people need to provide high quality care for a person with dementia.

Around 12,000 to 13,000 people are estimated to have dementia in Norfolk, but only around 40pc of those have been diagnosed.

Dr Neil Ashford, who is leading on the redesign of dementia services in Norfolk and Waveney, said: 'David Cameron's statements today about the importance of acknowledging and addressing the rising challenge of dementia care are very welcome. Norfolk and Suffolk NHS Foundation Trust is already in the advanced stages of redesigning its dementia care services to become a national leader. It is being supported by local commissioners, NHS Norfolk and Waveney, to raise diagnosis rates and deliver new services to people with dementia and their families.'

However, at a time of cuts to local councils' budgets for older people's social care, there is some concern that there is not the funding to be able to support the existing people who have been diagnosed with dementia, let alone all those who have not yet been diagnosed.

Willie Cruickshank, from the Norfolk and Suffolk Dementia Alliance, said: 'I think that what David Cameron has come up with is basically what we have been saying for 18 months and we should take pride in the fact we that in Norfolk and Suffolk we are ahead of the game.

'We welcome any extra funding for dementia care and research, but this isn't just about money. It's still going to be up to the people who deliver dementia care to work together better to achieve what we want.

'There is a long way to go with this silent crisis but things are a lot better than they were a few years ago.'

He said that unlike HIV and cancer, dementia will not have any high profile young rock stars with the condition who can help raise awareness, and there won't be any miraculous reovery stories taking up column inches in the national newspapers.

But the prime ministers speech is a step in the right direction, according to Mr Cruickshank, who said: 'He is helping to start the ball rollingin helping to reduce the stigma about it. We need to get people taking about dementia more.'

The alliance is taking part in this year's Dementia Awareness Week from May 20 to 26.