Britain’s new plastic banknotes are prone to sticking together meaning shoppers are at risk of handing over two at once, the Bank of England has admitted.

It has emerged that the polymer-coating on freshly made notes can affix to each other, proving irritating for people who accidentally end up paying twice when settling cash bills.

The first plastic tender to enter circulation will be a new £5 note featuring Winston Churchill, which is being unveiled on Thursday ahead of its launch in September. Today’s paper £5 notes will be formally withdrawn before the new polymer £10 note is introduced in 2017.

Experts warned the move to plastic notes could create a particular financial burden for elderly people as they are most likely to use cash, but may not notice their notes sticking together.

An official Bank of England Q&A sheet warns: “Brand new polymer notes can sometimes stick together, but this effect is short-lived once in use.”

Britain is joining a list of more than 30 countries that already use plastic banknotes including Australia which adopted the notes in 1988, as well as Singapore and New Zealand.

Unlike a traditional cotton paper banknote the polymer banknotes are almost impossible to tear, can survive a 90C washing machine cycle, and repel dirt and moisture. For example it is possible to pour a glass of red wine over one and wipe it clean.

Their durability means the notes are expected to last 2.5 times longer than today’s notes, meaning the Bank can cut costs over the long term by printing fewer.

However polymer banknotes begin to shrink and melt at temperatures above 120°C, meaning they can be damaged by an iron or a very hot washing machine or tumble dryer cycle.

To make them last longer, Mark Carney, the Governor of the Bank of England, is urging people to store the notes flat in their wallets, rather than folding them which he says could damage the plastic.

Justin Urquart Stewart, economist and founder of Seven Investment Management, condemned the move to plastic notes as a “waste of time”.

He said: “Given they have already been used in Australia and other countries it is frustrating that the Bank hasn’t developed the technology to stop plastic notes sticking together.

“It is likely to impact older people who might not be able to see they have paid with two notes instead of one, while younger people who use contactless cards will be unaffected. The move to plastic is a waste of time because soon most people won’t be using notes anyway, so frankly, the Bank of England ought to think again.”

In 2015 cash was used for less than half of all payments by consumers, with debit cards and contactless payments set to overtake cash payments by 2021, according to Payments UK, which represents banks, building societies and payment providers.

A polymer £10 note, featuring the author Jane Austen, will enter circulation next summer and the £20 note, featuring the artist JMW Turner, will be launched by 2020.