A vegan group's "misleading" advert linking cow's milk to cancer has been banned.

The poster by activists Viva! triggered two complaints to watchdogs after being seen on buses in Bristol last September.

The ad was banned following an investigation by the Advertising Standards Authority (ASA) because Viva! was unable to substantiate claims that hormones in cow's milk are linked to cancer.

The ad featured an image of a cow's udder and included the claims "Some dairy industry facts we bet you don't know … Most cows are pregnant when milking. That's why milk contains 35 hormones, including oestrogen … some of these are linked to cancer. Milk is for babies, so let Viva! wean you off the teat!"

Two people complained to the ASA that the ad's claim "milk contains 35 hormones, including oestrogen … some of these are linked to cancer" implied that drinking cow's milk could cause cancer, was misleading and couldn't be substantiated.

Viva! said the claim referred to hormones that were naturally occurring in cow's milk, which increased during pregnancy and were essential for calf development.

The campaign group said the claim did not refer to hormone treatments or artificial hormones.