Supplies of the famous copper-plated 2p coins are eight times above target, while stocks of their £2 sisters are 26 times above above where they need to be.
Over the past decade the volume of cash payments has plummeted 59 per cent, with cash accounting for six in 10 transactions ten years ago against just three in 10 last year. Forecasters suggested this could fall to one in 10 by 2028.
The coronavirus pandemic “may accelerate that trend”, the spending watchdog warned. Market demand for coins and notes from cash centres sunk by 71 per cent during the first month of lockdown, although this has since begun recovering.
Meanwhile, AGMs tailed off by 17 per cent in the two years to December 2019 to around 45,000.
While many old coins returned to circulation when the 12-sided £1 coin was introduced in March 2017, demand for bank notes has been rising. Some £50bn worth of notes have been lost in circulation, kept off the radar of transactions or savings.
The Treasury has committed to protecting access to cash, but the NAO joined the Commons’ powerful Public Accounts Committee in warning those who rely on cash in society risk being left behind.
Gareth Davies, head of the NAO, said: "The approach is fragmented, and it is not clear that the action being taken will keep up with the pace of change.
"As society progresses towards the wide use of digital payments, the use of cash in transactions is dwindling.
"It may become harder for people to access cash when they need it and those without the means to pay digitally will struggle if cash is not accepted."