More people fear being diagnosed with the debilitating brain condition above anything else than fear cancer or death itself, research shows.

A million people in Britain will suffer some form of dementia within two decades, and one in three pensioners will die with it, figures suggest.

Yet 12 times as much is spent each year on cancer research, and there are six times as many scientists working on how to treat tumours. Currently, as many as two-thirds of people who develop dementia are never diagnosed while the best treatments can only help reduce symptoms and cannot prevent the degenerative disease progressing.

At the launch of a campaign by Alzheimer’s Research UK to increase the “pitifully low” investment in dementia, Sir Terry Pratchett, the author, said: “Alzheimer’s is a large number of small tragedies usually played out behind closed doors, so in spite of the numbers living with it, the world still doesn’t take much notice.

“when the world was shocked by HIV in the Eighties, we saw a crash programme of research which has helped tame it enormously. We need the same kind of aggressive action on dementia now.” he is the charity’s patron and has early onset Alzheimer’s.

Currently 820,000 people in Britain are thought to suffer dementia, progressively losing their memory and struggling to cope with everyday activities. The most common cause is Alzheimer’s disease.

A million people are likely to develop the condition within the next 15 years as the population ages and 1.7 million will be living with it by 2051, placing a significant burden on informal carers, the NHS and care homes.

A YouGov poll of more than 2,000 people found that 31 per cent feared dementia the most as they grow older, compared with 27 per cent who were most scared of cancer and 18 per cent who feared death itself more than anything. Alzheimer’s Research UK, formerly known as the Alzheimer’s Research Trust, reckons that dementia costs the economy £23 billion a year, more than cancer (£12 billion) and heart disease (£8 billion) combined.

Yet it says only £50 million a year is spent searching for better diagnoses and treatments, compared with £590 million spent on cancer research and £169  million on heart disease.

Researchers are trying to perfect a simple blood test for Alzheimer’s, as early diagnosis is likely to lead to better management of the condition.

Several types of drug exist to help sufferers but they only treat the symptoms while the process of brain degeneration continues. Alzheimer’s Research is now appealing to the public, ministers and private companies to help increase investment.

Rebecca Wood, its chief executive, said: “Public concern around dementia is at an all-time high, yet dementia research is still the poor relation.

“We have such brilliant research talent in the UK which could make real inroads into defeating dementia with more support.”

She said that the charity funded hundreds of leading scientists with the help of public donations, but that even combined with government spending the effort still lagged far behind that made against other diseases.

Jeremy Hughes, chief executive of The Alzheimer’s Society, added: “Dementia is the biggest challenge facing the UK and people are right to be worried. it is a devastating condition that robs people of their lives. yet with the right treatments and support it is possible to live well with dementia. We must gear up to tackle this challenge by investing in research and support or else face a dementia catastrophe.”

Paul Burstow, the care services minister, agreed. he promised government help for research into its “care, cure and cause”.

He added: “The Department of Health’s research budget is nearly £1 billion this year – I want more of that funding to be supporting dementia research. But we can only do that if the number and quality of the research proposals are of the right standard to justify the investment.”