Millions of people who rely on their family or friends to manage their finances cannot access some of the best savings rates because the banks offering them will not recognise a power of attorney.

Four of the five best one-year fixed bonds are from banks or savings platforms that do not allow accounts to be opened by someone acting as an attorney. Nor can they open an account offering the best two, three, four or five-year fixed-rate bonds.

A power of attorney gives a trusted person — the attorney — the authority to manage someone’s affairs if they cannot do so themselves. An ordinary power of attorney gives someone the power to look after your affairs for a temporary period, if you are living abroad, for example. A lasting power of attorney allows them to manage your affairs permanently if you have lost mental capacity. There are two types: health and welfare, and property and financial affairs.

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There were 6.85 million powers of attorney registered at the end of 2022-23, according to the Office of the Public Guardian.

Anna Bowes from the comparison website Savings Champion said: “It’s very frustrating that not all savings accounts can be opened using a power of attorney because cash is often an important asset for short-term needs. It is unfair to penalise people who can no longer manage their own finances. It can also be complicated and time-consuming to open an account using a power of attorney since requirements can differ from bank to bank.”

The best one-year interest rate is 5.22 per cent from National Bank of Egypt, available through the savings platform Raisin UK, which also offers 5.21 per cent from Ziraat Bank. But Raisin does not accept applicants using a power of attorney, nor does the Access Bank UK, which pays the third-best rate of 5.2 per cent. Between them they have the best rates on one to five-year fixed bonds.

The best one-year fixed bond you can access using an attorney pays 5.15 per cent, from Union Bank of India UK. Raisin has six other one-year bonds paying at least 5 per cent, and two of the five best three-year bonds.

Raisin also has the best four and five-year bonds, at 4.75 per cent from the Turkish bank Isbank. An attorney wanting to lock in money for four or five years would have to settle for 4.31 per cent from Oxbury Bank over four years and 4.56 per cent from Hodge Bank over five, which would make them £44 or £19 less interest a year on £10,000 respectively, compared with Isbank’s bond.

Steven Amos, the chief executive of Raisin UK, said: “The marketplace lets customers manage their own accounts, and given this our systems can’t accommodate the processes required for others to manage them.” The Access Bank was approached for comment.

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Steven Amos, the chief executive of Raisin UK, said: “The marketplace allows customers to manage their own accounts, and given this our current systems can’t accommodate the processes required for others to manage accounts.” The Access Bank did not respond to a request for comment.

Having a restricted number of accounts to choose from can cause problems for attorneys managing large amounts and wanting to spread deposits across many banks. Under the Financial Services Compensation Scheme the first £85,000 deposited in a bank or building society is protected if the firm fails.

Anyone relying on an attorney may have more luck with regular savings accounts. Only one of the 30 best easy-access accounts, paying 5 per cent from Hoist Savings and again offered through Raisin, was not open to someone applying with a power of attorney.