Britons are being urged to spend or bank their old £1 coins before they become worthless later this year.

The new-look 12-sided £1 will come into circulation across the UK on Tuesday and shops have been told to stop accepting the traditional round coins on 15 October.

Ministers are reminding the public of the importance of all old coins being returned before the date when they lose their legal tender status.

“Our message is clear: if you have a round one pound coin sitting at home or in your wallet, you need to spend it or return it to your bank before 15 October,” Baroness Neville-Rolfe, commercial secretary to the Treasury, said.

Experts issued similar warnings last month.

Hannah Maundrell, editor in chief at Money.co.uk, told The Independent: “It’s craziness that £1 coins as we know them will soon become worthless. The chaos it’s going to cause for businesses is just part of the problem; it sends a bad message about saving to the many children that will be left disappointed when they find the £1 coins they’ve squirrelled away in their piggy bank are worthless. With more of us using cards and contactless payments to pay, the worth of going to all of this effort to replace what soon could be a redundant medium is questionable.

“You can get your bank to trade £1 coins for notes as long as they’re in bags of 20. If you don’t have this much sitting around you can just pay them into your bank or savings account and draw them back out in note form. Don’t use coin machines to swap them as they’re likely to charge.”

Martin Lewis from the MoneySavingExpert website, wrote: “There may be a few months left to sort it out, but it’s worth doing now as it’s all too easy to squirrel money away in piggypanks and forget about it.

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“Carting a bag of coins to the bank is a real faff – particularly if there isn’t a branch near you. So it’s much better to spend them now.”

The Government estimates around a third of the £1.3 billion worth of coins stored in piggy banks or savings jars around the UK are denominated in the current £1 coins.

Some of those returned by the public will be melted down and used to make the 12-sided version.

The new coin was announced in the 2014 budget and has been described by the Royal Mint as “the most secure coin in the world”.

It features the national flora of the UK’s four countries emerging from a coronet.

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