The UK’s leading Alzheimer’s charity has released new data showing wide variation in the rates of diagnosis across England.

The report, by The Alzheimer’s Society, records that just 31.6% of people with dementia are being diagnosed in the East Riding of Yorkshire, whilst 75.4% are being diagnosed in Islington.

But the proportion of people with dementia who have a formal diagnosis has increased to 46%, compared with 43% in 2011. The Alzheimer’s Society estimates, however, that there are 428,000 people in the UK who are living with dementia but haven’t been diagnosed.

Jeremy Hughes, chief executive at Alzheimer’s Society said: “It’s disgraceful that more than half of all people with dementia are not receiving a diagnosis, and disappointing to see such a disparity in diagnosis rates in different regions of the UK.

“This goes against best clinical practice and is preventing people with dementia from accessing the support, benefits and the medical treatments that can help them live well with the condition. Studies show that an early diagnosis can save the taxpayer thousands of pounds, because it can delay someone needing care outside of their own home.”

The Society has produced an interactive map highlighting the number of people who have a diagnosis of dementia in different Primary Care Trusts in the UK, and can be found here.

Predicted levels of dementia across the UK were compared with data from GPs on the actual number of patients being diagnosed. The map suggests a north-south divide, with the highest rates of diagnosis in Scotland (average 64%) and Northern Ireland (average 63 per cent).

Rates dropped to 50% in the north-east of England, 41% in the south-west of England and 39% in Wales.

Health secretary Jeremy Hunt, who is leading the UK Government’s push for greater dementia awareness, said: “The small improvement in the overall rate of dementia diagnosis is good news, but the extreme variation we see across the country is unacceptable.

“It’s time for the worst performing local areas to wake up to the dementia time bomb we are all facing. While many areas do excellent work, the worst is diagnosing just one third of people with dementia – delaying and preventing them from accessing vital treatment and causing unnecessary suffering.

“I have committed to making this a year of dementia awareness; improving both diagnosis and understanding of the condition are integral if we are to begin making a difference to people’s lives. As part of my commitment, I will shortly be visiting every region to meet with the people responsible in the health and care system to encourage them to make a difference.”