The Treasury has “paused” production of a new 50p coin commemorating Brexit on 31 October after it became clear that the UK is unlikely to leave the EU on time.

The special edition was supposed to mark Britain’s departure at the end of the month, but production by the Royal Mint has stopped and already-minted coins are being stockpiled.

A Treasury spokesman said: “We have paused production of the Brexit coin, and will take a final decision in due course.”

There has been speculation that the estimated 1,000 coins minted so far could fetch a premium on the 50p cover price, possibly selling for as much as £800 each.

The chancellor, Sajid Javid, had ordered 3m of the coins to be made ready for the end of the month with the inscription “Peace, prosperity and friendship with all nations”. Underneath the inscription, the Mint placed the historic date the UK is supposed to leave the EU: 31 October 2019.

Treasury officials refused to say whether the Mint will release the coins into circulation or seek to realise their inflated value by selling them on its website.

The chancellor could decide to melt them down to be remade with a new date but officials are unlikely to risk going ahead until parliament and the EU give further clarity.

Javid’s predecessor, Philip Hammond, had planned a limited edition of about 10,000 commemorative coins to be sold to collectors for £10 each in time for the first deadline on 29 March.

The 50p move is the Treasury’s second U-turn in 24 hours after it confirmed that it had pulled a budget due to be held on 6 November, when the government would have detailed its economic plans and tax and spending priorities.