The Bank of England is facing a potential legal battle after being accused by activists of dealing in "blood money" over its decision to keep polymer notes with traces of animal fat in circulation.
The central bank said it had carefully considered alternative options - like destroying or reprinting the £5 note and delaying the issue of the £10 note set for September - but said it would be costly and compromise new anti-counterfeit measures.
Activist Doug Maw - a 48-year-old from Keswick in Cumbria who collected over 134,000 signatures calling for the recall of new £5 notes in November - said he was "quite angry" about the news, and is now teaming up with the National Council of Hindu Temples (NCHT) to explore legal options.
He told the Press Association: "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."
It comes just weeks after bank staff met with Mr Maw and the general secretary of the NCHT to discuss the issue.
The decision also drew ire from animal rights group PETA, which said: "The Bank of England is effectively dealing in blood money, and while it's not the most shocking case of cruelty to animals, there's no excuse for subsidising abattoirs to make a banknote."
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 at the end of March 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 has already spent £24 million on printing 275 million new £10 polymer notes since production began in August, 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 the destruction of those notes would cost a further £50,000, the Bank said.
"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."
But NCHT general secretary Satish K Sharma said the move signalled a "loss of religious and ethical freedom" and was "very problematic".
He explained that it would hurt fundraising at temples which forbid animal products, and impact ceremonies where low denomination banknotes are given as part of a blessing.
Most Hindus are practising vegetarians and avoid using materials with traces of animal products, especially beef, as the cow is considered religiously sacred.
Mr Sharma said: "Knowing the ethical dilemmas for vegetarians and vegans, and the religious dilemmas that the Hindus, Sikhs and Jains are now being plunged into by their actions, they (the Bank) still chose not to make the changes.
"I think that's an unpleasant response. In this day in age that really isn't the way in which our governmental institutions and national institutions should be behaving."