Britain to issue new one-pound coin modelled on threepenny bit

 (Reuters) - Britain plans to replace its 1-pound coin with a new version modelled on the country's historic threepenny piece, Chancellor George Osborne will announce later on Wednesday.

The new pound's proposed twelve-sided shape composed of two different coloured metals will help with efforts to crack down on fake currency, the finance ministry said.

"After thirty years loyal service, the time is right to retire the current 1-pound coin, and replace it with the most secure coin in the world," Osborne said in a statement.

He will formally notify Britain's MPs of the proposed new coin, to be introduced in 2017, as part of his annual budget announcement in parliament.

The current pound has become vulnerable to sophisticated counterfeiters, the finance ministry said, with about 3 percent of all 1-pound coins, or 45 million, believed to be forgeries. That figure rises to 6 percent in some parts of the country.

The new coin will be armed with new Integrated Secure Identification System (iSIS) technology developed by the Royal Mint, the maker of Britain's coins whose history dates back over 1,100 years.

"We think it's suitably British," the Royal Mint's director of circulation Andrew Mills told BBC Radio. "It's very reminiscent of two other British coins. The twelve-sided shape is very reminiscent of the threepenny bit and secondly, of course, it doesn't look that dissimilar to the 2-pound coin."

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

A public consultation will be held over the summer to consider the metal composition and to weigh up the impact of the new-shaped coin on different stakeholders such as vending machines operators.