SUPERMARKETS will fling open their trolley bays as workers get to grips with adapting slots to fit the new £1 due to be rolled out today.

The 12-sided £1 coin enters circulation on Tuesday as it starts to edge out the old "round pound" after more than 30 years amid concerns over the number of fakes in circulation.

The new coin has been described as the most secure in the world and boasts high-tech features, including a hologram.

However, old pound coins will be legal tender until October.

Consumers craving a snack or trying to park may face confusion when they attempt to pay at coin-operated machines, as some will not immediately accept the new coin.

They may find themselves rifling through their wallets for an old round pound.

Tesco trolleys across many of its stores will be unlocked as the supermarket giant performs upgrades so that they can accept the new coin.

A Tesco spokesman said last week that "fewer than 200" of its stores will be affected.

He said last week: "We will continue to have colleagues on hand to attend trolleys in our stores, so our customers aren't affected by the changes."

The old coin and the new coin will co-exist together for a period of around six months, until the round pound ceases to be legal tender on October 15.

The new coins have been made at the Royal Mint in Llantrisant, South Wales, at a rate of three million per day.

They have a gold-coloured outer ring and a silver-coloured inner ring and are based on the design of the old 12-sided threepenny bit, which went out of circulation in 1971.

The Automatic Vending Association (AVA) estimates that when the new coin goes into circulation, around 85% of vending machines will be able to accept the new £1 coin and all will still accept the old coin.

It said that with around half a million vending machines across the UK, ensuring all of them are upgraded is a "major operation".

The body has estimated that all vending machines will be fully upgraded by the end of the transition period on October 15.

Jonathan Hart, chief executive of the AVA, said the upgrades needed for the new £1 coin will cost the vending industry an estimated £32 million.

He said: "We support the Royal Mint and the Treasury's actions to protect the integrity of currency in the UK and reduce the level of fake coins in operation."

Savers and coin hoarders have also been advised to open their piggy banks and dispose of any old pounds either by taking them to a bank or spending them.

Steve Nowottny, news and features editor at MoneySavingExpert.com, said: "This is an important warning for dedicated savers and spare-change hoarders alike. Empty your piggybanks, upend your coin jars and scrabble behind the sofa to get all your pound coins together – then spend or bank them before October.

"Of course, you’ve a few months left yet to sort it. But it’s worth doing it now, with piggybanks and coin jars in particular it’s all too easy to squirrel money away and forget about it altogether."

Around £1.3 billion worth of coins are stored in savings jars across the country, and the current £1 coin is thought to account for nearly a third of these.