(REUTERS) - Britain plans to replace its 1-pound coin in 2017 with "the most secure coin in circulation in the world" as it cracks down on fake currency, the finance ministry said on Wednesday.

The design of the current pound coin, which has been in circulation for more than 30 years, leaves it vulnerable to sophisticated counterfeiters, the Treasury said.

"The Royal Mint estimates that about 3 per cent of all 1 pound coins, or 45 million, are now forgeries. In some parts of Britain, it is as high as 6 per cent." The new two-coloured coin, designed to have 12 sides like the pre-decimal three-pence piece or "threepenny bit", will be armed with the Royal Mint's new Integrated Secure Identification System (iSIS) technology.

iSIS has three tiers of banknote-strength security and can be authenticated via high-speed automated detection at all points within the cash cycle, the Treasury said.