Nearly 20,000 people have signed a petition called for 'pony painting parties' to be banned.
The craze - which the petition on change.org describes as 'disturbing' - is becoming increasingly popular, according to reports, despite the negative implications for the animals involved.
"Imagine being tied up amidst shrieking laughter, unpredictable touching and having strangers smear your hair in paint. Would you trade places? This is happening all over the country to horses right now and we need to take a stand," the petition, started by Sophie Tomlinson, from Altrincham, Trafford, says.
Tomlinson's petition follows a Facebook post by campaigner Joe Callister who publically shared images of a pony party on Facebook, calling the event 'disgusting, disrespectful and unjust'.
The petition has gained huge momentum since its launch on earlier this week - as well as garnering the thousands of signatures, it has sparked stories in the mainstream media and on BBC radio.
It has provoked a strong reaction in many of those who have signed it, with one person commenting: "How can this be allowed to happen? Absolutely disgusting, poor ponies. Children should not be painting animals for enjoyment!"
Another added: "This is just wrong - kids need to learn to respect animals not abuse them."
Campaigner Joe Callister, whose photos (above) sparked the petition, told Plant Based News: "It is morally wrong to exploit and objectify animals for our frivolous desires. Ponies are not chalkboards, just as much as elephants, dolphins, or monkeys.
"It is abusing power, It is shameful, disrespectful and unjust to use other animals like a chalkboard as a money-spinner, for therapy, education or any other reason when we have viable alternatives.
"I am not suggesting this is a welfare concern when painting, moreover I am bringing to light that it encourages an attitude that sentient beings are just some “thing” for our entertainment amongst other things."
'Ponies aren't props'
Elisa Allen, Director of PETA UK, told the Manchester Evening News: "Allowing kids to treat animals like colouring books is a lesson in insensitivity to which no thoughtful parents would expose their children.
"Ponies and horses aren't party props - theyre intelligent, complex animals who should be appreciated for their natural beauty. They're also sensitive and easily spooked – a child might even be kicked by a stressed pony who has been forced into a party environment with loud music and excitable kids.
"Animal exploitation has no place at a children's party, and PETA urges parents to opt instead for cruelty-free activities - like finger painting or face painting."