There are eight million so-called 'zombie' bank accounts in the UK, with a total of £1.2 billion of forgotten money sitting in them, according to new research by Compare The Market.

That means each account has an average of £141 of forgotten cash.

It found more than one in three people (37%) have multiple current accounts, but almost half (49%) only use one of them day-to-day.

So how do you find out if one or more is yours and how do you go about reclaiming the money?

Why do we have so many current accounts?

One in five admitted they had opened an account a long time ago and couldn’t be bothered to close it down.

More than half of the people surveyed said that they opened another current account to take advantage of the different rewards offered by different deals.

Worryingly, even though most of us (81%) use online banking, more than one in 10 (12%) people with multiple current accounts admit they check their unused accounts as little as twice a year.

By not regularly checking accounts you are less likely to spot signs of suspicious activity and keep track of your money – making them an easy target for ID thieves and hackers.

If you use any of the accounts for recurring Direct Debits, you could also be caught out.

By not monitoring the amount leaving the account you could end unwittingly using an unarranged overdraft and incurring charges if the Direct Debits are higher than anticipated.

By not keeping tabs on all your pots of cash you are also risking missing out on better deals for your money. So make sure you keep all your cash in a top-paying account.

Earn more from your money: compare high-interest current accounts

How to reclaim money in old bank accounts

If you still have your current account details, all you need to do is get in touch with the bank or building society to reclaim your cash and close unused accounts.

If you can’t remember your details you can use My Lost Account, which is a service offered by the British Bankers' Association (BBA), the Building Societies Association and National Savings & Investments (NS&I) to trace it.

This offers free guidance on recovering money from so-called ‘dormant' (unused) accounts.

Dormant accounts refers to those which have been inactive for 15 years and where the bank running the account has been unable to make contact with the account holder.

To prevent fraud or ID theft once an account has been declared dormant it can no longer be operated.  

Many people lose track of accounts when they move home but forget to inform all the banks they save with.

It doesn't matter how old the account is or how small you think the balance may be, and even if the bank has changed its name in the interim, My Lost Account could still help.

Money which has been left in dormant accounts for more than 15 years is now moved into a reclaim fund where it'll be used to finance charity projects. But even after this has happened your money can still be retrieved.

[Read more: Pension Tracing Service expands to meet growing demand for lost pensions]