A charity has called for better safeguarding for vulnerable dementia patients after it discovered that 15% of patients are cheated out of their cash.

The Alzheimer's Society said that up to 112,500 people living with dementia have been victims of "financial abuse" as a result of cold calling, scam mail, or mis-selling.

A new report by the charity found that almost two-thirds of carers said the person they look after had been approached by unexpected salespeople on their doorstep, while 70% were regularly targeted by telephone sellers.

The charity, which estimates the financial cost of the abuse amounts to more than £100 million, is calling on trading standards and banks to do more to help dementia sufferers, saying they should appoint "dementia champions" to help increase awareness about the condition.

Alzheimer's Society chief executive Jeremy Hughes said: "We are merely scratching the surface of the frightening hidden depths of financial abuse. Too often con artists are dealing another body blow to people who already face high care costs and a society that fails to understand their needs.

"It's only by working together with banks, local authorities, and of course the general public that we can turn this around and start the new year with new hope."

Martin Lewis, founder of MoneySavingExpert who wrote the foreword for the report, added: "The scale of this problem is huge. It's deplorable that people are prepared to take advantage of some of the most vulnerable in our society. What's more, the true amount of money lost is likely to be much higher as financial abuse often goes unreported. Society must help protect people with dementia - something must be done."

The study, conducted on 104 carers and 47 people with dementia, also found that three-quarters of patients have encountered difficulties when managing their money.

A charity spokesman said the best ways for sufferers to deal with money management include: talking to family about finances, setting up a lasting power of attorney, meeting with local bank managers, putting a "no cold callers" sign on their front doors and signing up to the Mailing Preference Service and the Telephone Preference Service register.

Mehboob Khan, chairman of the Local Government Association's safer and stronger communities board, said: "Exploiting vulnerable residents who are already struggling to manage their money simply won't be tolerated by councils. Our trading standards teams across the country are working hard to stop rogue trading and put right some of the stress, exhaustion and frustration these crimes can cause."