Households are being warned to spend or bank all their round pound coins before October, when they will cease to be legal tender.

They will be phased out from March 28, when the new 12-sided £1 coin hits the streets, the Government has announced.

And around the same time, new coin designs will start appearing in the shops, including a Jane Austen £2 and a 50p celebrating Sir Isaac Newton.

New coinage: The new £2 commemorating the Royal Flying Corps; the new Jane Austen £2; the new Sir Isaac Newton 50p; and the new 12-sided £1 coin (from left to right)

About £1.3billion worth of coins are stored in change jars up and down the country, and the current £1 coin accounts for nearly a third of that, the Government said.

Households must 'copper up' and either spend or deposit them before 15 October or lose out.

Replacing £1 notes, £1 coins were first launched on April 21, 1983. The Royal Mint has produced more than 2.2billion round pound coins since that time.

But there have been concerns about round pounds being vulnerable to sophisticated counterfeiters. Around one in every 30 £1 coins in people's change in recent years has been fake.

The new £1 coin, which resembles the old threepenny bit, has been hailed as 'the most secure coin in the world', with features including a hologram.

Some of the round £1 coins returned by the public will be melted down and reused to make the new £1 coin, which was announced in the 2014 Budget.

A Jane Austen £2 coin will celebrate the Pride And Prejudice and Sense And Sensibility author, while a Sir Isaac Newton 50p coin will mark the achievements of one-time Master of the Royal Mint.

Also arriving in the spring, the Royal Mint has announced a £2 coin design that will remember the Royal Flying Corps and its contribution to the defence of Britain's skies in the First World War using new aircraft technology. In 1918 the Royal Flying Corps became the Royal Air Force.

And a Jane Austen £2 coin will celebrate the Pride And Prejudice and Sense And Sensibility author, 200 years after her death.

A Sir Isaac Newton 50p coin will mark the achievements of one-time Master of the Royal Mint, whose wide-ranging work paved the way for the introduction of the 'gold standard' system for valuing a nation's currency.

The new £1 coin is made of two metals, with a gold-coloured outer ring and a silver-coloured inner ring. It has an image that changes from a '£' symbol to the number '1' when the coin is seen from different angles. It also has very small lettering on both sides of the coin and milled edges.

It will feature the flora of the four nations of the UK emerging from a coronet and is thinner and lighter than the round pound, but its diameter is slightly larger.

Heritage: The new £1 coin will feature the flora of the four nations of the UK emerging from a coronet, while a £2 coin design will remember the Royal Flying Corps

Announcing the date when the new coin will enter circulation, Chief Secretary to the Treasury David Gauke said: 'March 28 should be an important date in everybody's calendar this year - as we will have a new quid on the block.

'This is a historic moment as it's the first time we've introduced a new £1 coin since 1983, and this one will be harder to counterfeit than ever before.

'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 October 15.'

Businesses handling cash have been planning and preparing for the new coins.

Helen Dickinson, CEO of the British Retail Consortium, said there will be a transition period during which some vending systems may only be able to accept the old coin.

She said: 'Through the British Retail Consortium, most major UK retailers have been engaged in discussions and planning with the Royal Mint and Her Majesty's Treasury since the March 2014 announcement that a new pound coin would be introduced in 2017.

Deadline: Retailers will stop taking the old pound coins on 15 October 2017.

'Our aim is to ensure that the implementation of the new coin runs as smoothly as possible for our customers and staff. Our combined input into the project means we're confident the new coin will address the issue of counterfeit coins for businesses and the general public alike, and will prove highly secure for customers to use.

'While there will be a natural transition period where some vending systems may only be able to accept the existing pound coin, our industry is committed to ensuring we're fully prepared ahead of the launch in March.'

Association of Convenience Stories chief executive James Lowman said: 'The introduction of a new £1 coin is a positive step toward taking counterfeit coins out of circulation.

'It is essential that retailers are prepared for the introduction of the new £1 coin, as the transition is likely to affect a number of areas of their business especially if they have coin-operated machines such as self-service tills in store.