Vegetarians and vegans have reacted with fury after it emerged the Bank of England used animal fat to make its new £5 notes.
More than 50,000 people have signed a petition against the "disrespectful" use of tallow to manufacture the new polymer notes, which were released in September.
Some have threatened to boycott the plastic £5 notes and said they would "refuse" to use them.
The Bank of England pointed out that tallow is also used to make candles and soap.
Doug Maw, of Keswick in Cumbria, who started the petition against the use of tallow in the new £5 notes, said he has been left "disgusted".
"I understand old notes contain stuff as well - we can't do anything about what is in circulation - but the fact they are producing new ones is what really riles me.
"There is no excuse for it. There has got to be other ways of making money without using animal products.
"I don't think anything will happen about what has already been made, but I just hope they produce new ones without using animal fats.
"Can't they come up with something a little bit more modern? We are being forced to have animal products on us."
The 47-year-old hotel worker said he has started a second petition on the UK government petition site, which is awaiting authorisation, in a bid to get the issue debated and addressed in parliament.
A spokeswoman from the Bank of England said: "We can confirm that the polymer pellet from which the base substrate is made contains a trace of a substance known as tallow.
"Tallow is derived from animal fats (suet) and is a substance that is also widely used in the manufacture of candles and soap."