An animal rights website has published the names, addresses and phone numbers of farmers involved in the forthcoming badger cull to combat bovine tuberculosis.
A group calling itself the Coalition of Badger Action Groups is behind the website.
It said its intention was to watch farms that are involved in the cull, to make sure they are following biosecurity and animal welfare laws.
"Basically, if you're a farmer and involved in this cull, expect to be under a microscope," the website says.
The website includes details of three farmers it claims are organising syndicates that will be responsible for culling badgers in Somerset and Gloucestershire.
Maps of the culling zones are also on the website.
Contact details for the farmers - including their addresses, mobile phone numbers and email addresses - are published on the website alongside their names.
"These people are the ones who will organise the cull and employ the shooters and take the money from the farmers for doing it. They are ultimately responsible for killing our badgers," it says.
The website urges supporters: "Please spend a few minutes contacting these people and let them know your views on the badger cull.
"Please keep it polite, we are planning protests outside their business's [sic] please email in if you would like to be involved."
The website says both cull syndicates have based their companies at NFU headquarters, which it describes as a "union of the richest farmers and agri-corporate entities".
The NFU said it was investigating how details of the farmers became public.
NFU policy director Martin Haworth said: "We are very disappointed this has happened and we are doing everything we can to support and protect those individuals that have been named.
"We will do everything we can to find out how this information came to be released, and we will ask DEFRA and Natural England to investigate as well, so we can find the source of this information."
More on this topic
Read more about the cull on our dedicated badger cull and bovine TB page.