Saving account holders could earn an extra £7.7bn a year by checking the interest rate paid on their savings (AER) and then switching to a better deal, according to Moneysupermarket.

The comparison site is challenging all savers in the UK to call their banks this week and check their savings rate.

Millions of savers have money languishing in accounts paying dismal rates, with some discontinued accounts (accounts no longer offered to new customers but kept running for existing ones) paying as little as 0.25% AER.

A five minute phone call could potentially boost their savings interest by £200 per year if they end up moving their money to a higher paying account (perhaps with another provider) – it could be the best paid five minute call they’ll ever make.

Research by Moneysupermarket has found that 31% of all savers have never even checked their savings rate and could be earning practically nothing on their hard earned cash. Nearly half of all savers have never changed their saving account. Of these, 48% have held their account for over a year so the rate will probably be significantly lower than when they opened their account – something they may not be aware of.

Kevin Mountford, head of savings at Moneysupermarket, said: “Many people stick with the same bank for a lifetime, and our findings show a third of savers opened their account over 10 years ago. But when it comes to savings this could be a big mistake.

“We are calling on everybody who is at all unsure about the return they are getting on their savings to contact their bank this week and check their savings rate directly. When times are tough, a simple action like checking the interest rate on your savings can pay dividends.”

Half of Brits who have checked the interest rate since taking out their account have been disappointed to see it has gone down. However, even this has not been enough to shake them out of their apathy – with just a quarter having switched savings accounts to get a better interest rate in the last year.

Mountford continued: “The banks seem reluctant to make it easy for customers to know when the rate has dropped. The changes may be there in the small print, but as a quarter of savers only skim read the terms and conditions from their bank, and 15% read nothing at all, most will miss these all important announcements – something the banks no doubt rely on.

“Consumers need to take responsibility for checking rates either by reading statements clearly, or using their initiative to call their providers. For those with money in poor-paying accounts a quick phone call could be all it takes to find out your rate, and then visit Moneysupermarket to see how it compares to the best deals currently available. You should then move your savings and make your money work much harder for you.”