Easy access funds accounted for around 60% of all interest-bearing deposits before the introduction of the Funding for Lending Scheme in 2012, with the remainder in notice and fixed term accounts.

But now, as the scheme has closed, an estimated £724bn accounting for 81% of the market is languishing in easy access accounts.

According to independent savings advice site, Savings Champion, if savers don’t need access to their cash instantly, saving half of this money in a notice account means they could be earning over £4.6bn in extra interest. Plus, the cash can be accessed in just four months.

Anna Bowes, co-founder of Savings Champion, said: “Most people leave funds languishing with their high street provider, as they assume that moving it won’t earn much more interest. And as the high street providers don’t offer notice accounts, this could explain why many don’t know about or use these useful middle-ground accounts.

“But, with rates as low as 0.05% on the high street, if savers knew they could increase the interest they earn by as much as 1.70% – which equates to an extra £850 a year on a balance of £50,000 – and still have access to their funds within four months, surely it’s worth moving funds that aren’t needed immediately.”

In fact, rates on best buy notice accounts are at their highest level for two and a half years, and the choice is wider for savers.

The most common and best value accounts are from 60 to 120 days’ notice, although the very best rate is for 180 days, paying 1.77% gross/1.78% AER.

Bowes added: “Savers need to be aware of notice accounts in order to take advantage of them and even those who are familiar with the concept may not be familiar with the providers, as the most competitive accounts tend to be provided by lesser-known names such as Secure Trust Bank and OakNorth Bank.

“As long as the provider is protected by the FSCS, then why not take a well-informed leap of faith with an unknown provider, as it is definitely the challenger banks that dominate this market.”