Global Justice Now's Dan Iles said: "We felt like someone needed to do something to expose the truth to people who buy Monsanto’s products. And what better way to do this than using Monsanto’s own brand to insert some much needed facts into their marketing."
The pack, which includes spoof Roundup labels and leaflets, is designed to take to a Roundup selling retailer where campaigners are asked to "put the label onto a 1L Roundup spray bottle".
The label says the World Health Organisation has said the product is "probably carcinogenic" and also attacks corporatism.
Then Global Justice Now encourages supporters to take a photo and share on Twitter or Instagram.
Iles claimed that at the time of writing, "hundreds of packs have been ordered from all over the UK". Photos from some of these actions have already started appearing on social media, Iles said.
The European Food Safety Authority (EFSA) found in November 2015 that glyphosate is "unlikely to pose a carcinogenic hazard to humans". Meanwhile last week, the US Environmental Protection Agency (EPA) published its official classification of glyphosate as: "Not Likely to be Carcinogenic to Humans."