Retailers should be on the lookout for counterfeit £1 coins after the Royal Mint revealed that one in every 40 £1 coins is now a forgery – an increase from the one in 50 figure it reported only six months ago.

The Royal Mint’s latest study shows that 2.58% of coins on the market are fake, resulting in £37.5m-worth of counterfeit £1 coins currently in circulation.

Former chief assayer Robert Matthews warned that the number of counterfeit coins on the market could hurt independent retailers. “If the public starts losing confidence in coins and notes, you get people refusing to take them,” he said. “It could damage a lot of small shopkeepers.”

The area worst affected was Northern Ireland, with 3.6% of coins tested being forgeries.

Seamus McFadden, who owns McFadden’s Super Shop in Strabane, Co. Tyrone, says he now refuses £1 coins which he suspects are forgeries, after being caught out in the past.

“I’ve instructed my staff to refuse them whenever they are unsure,” he said. “The people we’ve refused all seem to have been unaware they had fakes and were caught out as well.”

Seamus has advised his staff to scrutinise the colour and inscription on the coins. He advised: “The fakes don’t keep their colour for long; the inscription on the side isn’t as clear; and the Queen’s head is also slightly off-centre on some.”