Ministers are attempting to shut down a website that discloses the names and home addresses of officials involved in the badger cull.
Two trial culls to shoot free-running badgers have been licensed in Gloucestershire and Somerset, with a third pilot, in South Devon, planned after that.
The Government-approved measure seeks to reduce tens of thousands of cattle slaughtered each year after becoming infected with bovine TB.
On the website, activists are urged to take direct action to disrupt the cull, including bombarding the named officials with unwanted phone calls and e-mails.
The home address of Owen Paterson, the Environment Secretary, is disclosed along with those of government officials and National Farmers' Union employees.
The personal details were first published on a British-based site, which is run by the Coalition of Badger Action Groups (CBAG).
They were removed after the site was served with an injunction, but within minutes had reappeared on the US-hosted site.
Campaigners are urged to "contact all the people involved as frequently as you can".
A warning letter has been sent by ministers to the US-based company that hosts the website, urging it to remove the material from the internet or face prosecution.
Supporters of the cull say it is essential to halt the spread of tuberculosis in cattle but the Government is concerned that intimidation could make some farmers pull out of it.
A spokesman for CBAG denied the groups were behind the US website, but added: "If you're an organisation in support of a cull on badgers don't be surprised if people start clogging up your mail."
Last week a poster urging people to call a mobile phone number with "secrets" about farmers involved in the controversial badger cull were put up around the pilot zone in Somerset.
The action follows a licence being issued by Natural England last week allowing farmers to shoot badgers in the area mainly in West Somerset and partly in Taunton Deane.
The number was originally posted on Stop the Cull's Facebook page alongside a request for information about those involved in the cull.
A spokesman for Stop the Cull said: "I don't think the posters are aimed at harassing farmers, but we need information about where the cull's going to happen."
