Nearly 50 million plastic £5 and £10 notes have had to be replaced since they were launched by the Bank of England due to wear and damage, according to new figures.
Around 20 million of the Bank's new polymer £5 notes, which have a portrait of Sir Winston Churchill on the back, have been replaced in the first three years since they were introduced.
And about another 26 million plastic £10 notes have also been replaced by the Bank in the two years since they were launched in September 2017.
The figures – revealed following a freedom of information request by the PA news agency – are likely to raise further questions over the durability of the new plastic notes.
They come after claims that some of the security features – including the Queen's face – can be rubbed off with pencil erasers.
It sparked fears that fakes were in circulation in 2017 after police came across notes that appeared to be missing the foil image of Big Ben, only to be told by the Bank that the feature had peeled away or been rubbed off.
There have also been reports the notes are particularly prone to domestic accidents – and can shrink to a quarter of their size if exposed to a hot iron while hidden inside a pocket.
Tea and red wine stains are another foe that can deface the new polymer notes, it has been claimed.
The Bank has since insisted its new plastic notes are "not indestructible", though the durability of the notes were a key plank of its move to swift away from the old paper fivers and tenners.
The Bank has claimed the plastic fivers will last two-and-a-half times longer than the paper ones.
Bank governor Mark Carney – who has spearheaded the introduction of the polymer notes – said in the Bank's most recent annual report: "The quality and security of banknotes are also central to monetary stability.
"Polymer notes are safer than paper notes, and last more than twice as long.
"They are also better for the environment due to both their longevity and recyclability," he added.
In response to PA's freedom of information request, the Bank said the damage so far to these plastic notes "mainly relates to folds, tears, holes and foil wear".
It said it was "consistent with the general wear" expected for bank notes.
The Bank also pointed out that the number of notes replaced were a small percentage of those in circulation, working out at up to 4% of the £5 notes in circulation in 2018 and 3% in the first nine months of 2019.
The number of plastic tenners replaces were under 2% of those in circulation in 2018 and 2019, it added.
But with the new plastic £20 note featuring artist JMW Turner due to be launched in 2020, the figures raise queries over just how long the polymer notes last.
The Bank said: "While we expect the polymer notes to have a longer life, it is too early in the note's lifecycle to yet understand the rate of replacement of polymer notes."