The Bank of England has bowed to vegans and some religious groups outraged their new £5 note, which was revealed to contain traces of animal fat.
The admission was made in a tweet by the Bank which confirmed the new plastic currency had small traces of tallow - a product typically made from beef or mutton.
Innovia, which supplies the product to the Bank of England - as well as New Zealand's Reserve Bank - is now working on "potential solutions" to the issue.
The company told the Bank its supply chain shows an "extremely small" amount of tallow at an early stage of making polymer pellets.
Those pellets are used to create the base substrate of the £5 notes, which have only been in circulation since mid-September.
The revelation sparked an online petition calling for the production process to be changed. It was signed by more than 112,000 people.
"The new £5 notes contain animal fat in the form of tallow. This is unacceptable to millions of vegans, vegetarians, Hindus, Sikhs, Jains and others in the UK," the petition reads.
"We demand that you cease to use animal products in the production of currency that we have to use."
In a statement, the Bank of England says it didn't know about use of tallow when the contract with Innovia was signed.
"We are aware of some people's concerns about traces of tallow in our new five pound note. We respect those concerns and are treating them with the utmost seriousness," it said.
"Innovia is now working intensively with its supply chain and will keep the Bank informed on progress towards potential solutions."
The polymer £10 is set to be introduced next summer, with the £20 due to be in circulation by 2020.