Britain will mint a new 50 pence coin to commemorate leaving the European Union in spring 2019, the finance ministry said.

The departure is one of a series of historic moments such as the 2012 Olympics, the decision to join the European Economic Community, the predecessor to the EU, in 1973, and the centenary of the First World War, it said.

"In line with this tradition, the Royal Mint will produce a coin to commemorate the UK leaving the European Union," it said.

The official coin.

The news came in a video on the finance ministry's Twitter feed in which a seven-sided silver-coloured 50 pence piece was seen with "Peace, prosperity and friendship with all nations," emblazoned on it, and Brexit day, "March 29 2019".

The announcement formed part of the annual budget.

Brexit continues to divide Britain, more than two years after a referendum that returned a 52-48 per cent decision.

Prime Minister Theresa May is struggling to reach agreement with the EU and her Conservative party and other rivals are also split on the issue.

News of the coin received a mixed reaction on social media.

"One side features the Queen with her head in her hand, quietly sobbing, while the other has a comprehensive list of the benefits the people of the UK will receive on leaving the EU," one user joked. The other side of the coin was pictured blank.

But one Brexit supporter suggested the coin should read "Free at last!"