The Bank of England has said that it will keep the £5 polymer note in circulation and issue a new £10 polymer note as planned, despite concerns from activists over traces of animal fats.
It confirmed that an "extremely small amount" of tallow was used to produce polymer pellets, which were then used to create the material for the £5 note.
The central bank said it had carefully considered alternative options - like destroying, reprinting and delaying the issue of the £10 note - but said it would be costly and compromise new anti-counterfeit measures.
"Weighing the considerations below, the Bank has now concluded that it would be appropriate to keep the £5 polymer note in circulation and to issue the £10 polymer note as planned, in September."
Fury among vegetarians and vegans erupted following confirmation by the Bank that the notes contained tallow back in November.
More than 134,000 people have signed a petition against its use, with activists advocating for a more suitable alternative.
However, the Bank said it has held off signing supply contracts for the £20 polymer note, which is due to be released in 2020, in order to weigh plant-based substitutes like coconut oil or palm oil.
It is launching a public consultation and will make a final decision on how £20 notes - and future runs of the £5 and £10 notes - will be manufactured by summer 2017.
The Bank said it would have incurred major costs if it decided to destroy and reprint existing notes.
It has already spent £24 million on printing 275 million new £10 polymer notes since production began in August.
That is on top of the £46 million spent on printing the £5 note.
Reprinting those notes using new materials would mean incurring those costs again, while destruction of those notes would cost a further £50,000.
"The Bank works hard to ensure that the public has enough secure notes to use in daily life and destroying the hundreds of millions of notes already printed would put this at risk," the Bank said in its report.
It stressed it would not be able to guarantee "sufficient stock" of paper notes if it were to destroy the polymer notes.
"Delaying the issuance of the polymer £10 would also delay the benefits of the increased counterfeit resilience of polymer being achieved for the Bank and the public."
Doug Maw, who started the petition against the use of tallow in the £5 note, said he was "quite angry" about the Bank's decision and was considering legal action.
It comes just weeks after the 48-year-old, from Keswick in Cumbria, met representatives at the Bank of England to discuss the issue.
He said: "The fact that they've decided to go ahead and not withdraw and continue (circulating the notes), means they are forcing people who have religious and ethical objections to use something that's against their religious beliefs and their ethical beliefs.
"I'm most definitely as of now looking at legal advice and we will definitely be bringing a test case against them because I'm pretty sure we will win it."