Hargreaves Lansdown said there is £267.8bn languishing in bank accounts paying no interest at all, costing savers up to £7.4bn a year, based on a 2.75% interest rate.
Research commissioned by the financial services company said that ditching the high street banks which offer low-interest rates could result in greater savings through a higher rate of interest.
Out of the 2,000 people surveyed, nearly half have not switched savings accounts in the past five years, while 35% of people have never switched.
According to the research, the most common reason for not switching was rates were too low to bother with, with 32% of respondents saying this.
Twenty-six per cent of people trusted their bank so did not want to leave, while 18% thought switching was too much hassle.
“Save your loyalty for your loved ones: your bank doesn’t deserve it. Sticking with a high street giant despite disappointing savings accounts paying miserable rates of interest, is costing us billions of pounds,” said Sarah Coles, senior personal finance analyst at Hargreaves Lansdown.