Five people were arrested by investigators probing a suspected major £1.2 million counterfeit coin operation.
Morning raids were carried out at six locations across Sussex by 90 officers from the National Crime Agency (NCA).
The Times reported that the arrests were part of an investigation in to the forgery ring that led to HM Treasury scrapping the £1 coin.
The coin is being replaced from 2017 by a 12-sided version considered to be the hardest in the world for criminals to copy.
The new version will replace the current £1 coin which has been in circulation for more than 30 years.
The Treasury has said that advances in technology have made the current £1 coin more vulnerable to counterfeiters.
The four men and a woman were detained at five separate addresses on suspicion of importation, money laundering and offences under the Forgery Act.
A Treasury spokesman said: “Over recent years, there has been an increase in the quantity of counterfeit £1 coins. The Treasury works closely with the Royal Mint, the National Crime Agency and the cash-handling industry to explore ways to maintain confidence in the currency and combat counterfeiting.
“After 30 years’ loyal service, we announced last year that the time is right to replace the current £1 coin with a new, highly secure coin that will reduce the costs of counterfeiting to our economy.
“The Government will ensure that the new design safeguards the integrity of our coinage for the future, and will employ the latest technology to make it the most secure circulating coin in the world.”