A quarter of a sample of 2,000 over-45s have access to a relative’s bank account who isn’t their spouse.

Of these, almost a tenth had a formal joint account with a relative and a fifth had access to a relative’s bank card or online accounts.

However, probate provider the Co-op, which carried out the research, said these informal arrangements often cause significant problems after death.

“The worst of the problems, and sadly one of the most regular, is where financial abuse is alleged to have taken place. This can add months, if not years, to the length of the probate process,” said Gavin Holt, head of probate at the Co-op.

“It’s concerning that so many people are ignoring, or perhaps are not aware of, the benefits of lasting powers of attorney.”

A lasting power of attorney is a legal document which allows trusted individuals to make decisions about your finances and your personal welfare if you become unable to make the decisions yourself.

(For more on why a lasting power of attorney matters, click here.)

The research shows a third of people had access to a parent’s bank account and a fifth to a sibling’s account. A tenth were able to access an aunt or uncle’s accounts, while a further tenth were able to access the account of a grandparent.

The main reasons for providing access to their money was to allow them to pay for groceries and luxuries such as holidays – things, that an appointed attorney could do legally and securely.

Over a tenth admitted that they’d worry about a relative borrowing money if they were short themselves and a further 5% said they had suspicions that their relative may have previously taken money.