Atom chief executive Mark Mullen said while current account customers may feel they are getting a free service, they pay a hidden cost due to poor interest rates. “Their business models rely on customer inertia and keeping those customers' savings in current accounts paying well below one percent.”

Savers can switch to lesser-known banks with confidence as the first £85,000 is fully protected under the FSCS.

Leaving money in current accounts exposes it to the full force of inflation, said Adam Thrower, head of savings at Shawbrook Bank. “It makes little sense when there are numerous competitive savings accounts available.”

Someone with £20,000 in a standard current account might earn £200 a year at best in a current account, and possibly much less, Thrower said. “The same sum in a market-leading one-year fixed rate Isa could earn 4.63 percent, generating interest of £926 a year instead.”

Savers can get more outside of an Isa, with one-year fixed rate bonds from Atom, Tandem Bank and United Trust Bank all paying 5.85 percent a year, generating £1,170 from a £20,000 deposit.

United Trust Bank pays a fixed rate of 5.90 percent for two years, worth £2,360 to those who can lock their money away for two years.

The big banks will never be on your side. Don't play their game by leaving excess funds in their accounts when it could work harder else.

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