LONDON • The United Kingdom's round pound coin will no longer be legal tender from October, allowing for a six-month transition to a new 12-sided version that will enter circulation on March 28.

Britons should aim to spend the coins or exchange them at a bank before the Oct 15 deadline in order to take them out of circulation, Chief Secretary to the Treasury David Gauke said yesterday.

The Treasury estimated that about 1.3 billion pound coins are in purses, wallets and jars around the country.

The new coin - the first reshaping of the pound since 1983 - is aimed at defeating counterfeiters who have put millions of fakes into circulation. The Royal Mint estimated in 2015 that 2.55 per cent of all pound coins were fake, or about £33 million (S$59 million).

"March 28 should be an important date in everybody's calendar this year as we will have a new quid on the block," Mr Gauke said. "This one will be harder to counterfeit than ever before."

The 12-sided design is based on the three-penny bit that was phased out in 1971, two years before Britain entered the European Economic Community, the precursor to the European Union.

The introduction of the new coin coincides with the end-March deadline that Prime Minister Theresa May has set for formally triggering Brexit talks. The Royal Mint aims to make more than 1.5 billion new pound coins in Llantrisant, Wales, at a rate of as many as 2,000 per minute.

Apart from having 12 sides, the coin will be two-toned, with a gold-coloured nickel-brass outer ring and a silver nickel-plated alloy inner circle. Alternate sides will be grooved, and the coin will have a hologram-like image that appears as a pound sign and the numeral 1 seen from different angles, as well as micro-lettering on the inside of the rim and a hidden, undisclosed security feature.

BLOOMBERG