The coin, which is intended to be the “most secure in the world”, draws inspiration from the design of the old 3d (3 penny) coin, which was in circulation between 1937 and 1971.
It will launch in 2017, and comes following concerns the 30-year old coin is becoming vulnerable to counterfeiting, with an estimated 45 million forgeries in circulation.
In a statement, the Royal Mint said: “The proposed £1 coin design is distinctly British, with a twelve-sided shape which evokes memories of the pre-decimalisation threepence piece.”
The coin will be made of two different coloured metals and contain security features in line with the Royal Mint’s currency security network, iSIS.
The public and industry stakeholders will be consulted on the proposals this summer. There will also be a competition for the design on the reverse, or ‘tails’, side of the coin.
Chancellor George Osborne is expected to officially unveil the new coin today, as he sets out his plans for the 2014/15 financial year.