New £1 coins are entering circulation with holes and blemishes despite being lauded as the most secure in the world.
Consumers have expressed confusion at being handed the recently released 12-sided pound with apparent minting problems.
Rolled out last month, the coin was boasted to have a range of high-tech features, including a hologram, which made it hard to counterfeit.
The issue was uncovered by The Sun newspaper and has seen some coins lose the silver centre, which features the Queen's head, entirely.
The Royal Mint said such "variances" were always likely to slip past its quality control due to the volume of coins being made at speed.
Warped pounds are now being auctioned online with starting prices as high as £5,000.
Shopper Tamzin Nye was handed the new coin as change but found it misshapen and with a gap between its gold outer ring and silver core.
"I just got confused at how it got out really, even if it is a fake it's meant to be an unfakeable pound coin for it to come out so quickly, or however it got out of the Royal Mint," the 18-year-old mother from Deal, Kent said.
Early teething problems have hampered the launch of the new design, including incompatibility with coin-operated machines and shopping trolleys.
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.
Three million of the modern versions have been made at the Royal Mint in Llantrisant, South Wales 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.
Last year former chancellor George Osborne claimed it was "the most secure circulating coin anywhere in the world" developed "with ground-breaking technology".
A Royal Mint spokeswoman said: "The Royal Mint produces around five billion coins each year, and will be striking 1.5bn new £1 coins in total.
"As you would expect, we have tight quality controls in place, however variances will always occur in a small number of coins, particularly in the striking process, due to the high volumes and speed of production."