The Treasury said the coin will bear the words "Peace, prosperity and friendship with all nations" and the date March 29, the day the U.K. is due to leave the 28-nation bloc after 45 years of membership.
The Treasury said the coin was part of a British tradition of "producing coins in order to commemorate historic moments." But opponents of Brexit were unimpressed with the gesture, and quickly filled social media with jokes, many playing on the negative impact leaving the EU could have on Britain's economy.
Opposition Labour Party lawmaker Wes Streeting tweeted: "Government unveils new coin worth 50 pence after Brexit," above a picture of a pound coin. The European Commission said it has no plans to release a special euro-coin to mark Britain's departure.