Vegan activists have published the names and locations of thousands of dairy farms across England and Wales.
Project Calf wants people to confront farmers and video their responses when questioned about dairy farm practices.
Those behind the campaign have published an online interactive map on their website to direct activists to up to 10,000 dairy farms in the UK.
Project Calf says: “The aim is to bear witness to the suffering of the animals on dairy farms and gather footage of what is happening to them to show people where their dairy products really come from.
“There are lots of options when it comes to choosing which equipment you want to use – hidden cameras, camcorders, regular cameras or even a drone. Or just use your phone.
“All footage will have an enormous and vital impact when documenting the horrific reality behind dairy.”
Project Calf asks its supporters to stay within the law and to film farms with public footpaths.
The farms on the map are registered with the Food Standards Agency and the information was already publicly available.
Project Calf says: “Locate a dairy farm using our maps. Using public footpaths, obtain the footage of the cows and separation pens.
“Talk to the farmers about dairy practices. Let the farmers know their dirty business is everyone’s business.”
One farmer, who commented on the map, said the campaign was “absolutely scandalous”.
Sally Reedman’s farm is listed, but she said she would happily give any activists a tour.
“We’ve decided if any come round they can have a welcomed guided tour. We don’t kill bull calves or sell them to market – they go to a local farmer who keeps them as fat beast – our cows are all of a good age, they don’t go into calf until they are 2 and have 18 months out to grass before joining the milking herd, our girls come to us for cuddles and are all happy and well.”