A best-selling herbicide that the World Health Organisation suspects causes cancer could get a new lease of life in Europe after being deemed safe by a key assessment based largely on classified industry reports.

A decision on whether to extend the license for glyphosate’s use in Europe is pending, but earlier this year, it was deemed “probably carcinogenic to humans” in a preliminary report from the WHO’s International Agency for Research on Cancer (IARC). The full report is due for release imminently.

Any revocation of the European license would hit the profits of Monsanto which manufactures the weedkiller which is often used in conjunction with GM crops.

Monsanto said it was “outraged” at the assessment and accused the WHO of “agenda-driven bias”. Sources at the European Food Safety Authority say that they may have to delay publication of their opinion on the safety of glyphosate to take the IARC report into account.

Now a key assessment by the German Federal Institute for Risk Assessments (BfR), seen by the Guardian, has drawn contrary conclusions from the IARC’s data. The BfR paper also relied heavily on unpublished papers provided by the Glyphosate Task Force, an industry body dedicated to the herbicide’s relicensing. Its website is run by Monsanto UK.

The BfR’s report found “very limited evidence of carcinogenicity” in mice exposed to glyphosate, and recommended its re-approval, with a relaxation in the acceptable daily intake from 0.3 to 0.5 mg per kilogram of bodyweight per day.

A BfR spokesperson said that another WHO working group had also concluded that glyphosate was not carcinogenic, and an expert task force would soon clarify the health body’s position. “At the moment, we haven’t seen the IARC’s full monograph so it is difficult to judge their work but we will look into it when it is available,” the official said.

The environmental NGO Greenpeace argues that any approval of glyphosate while doubt remains would violate the EU’s precautionary principle, which obliges regulators to err on the side of safety, and undermine public trust because there has not been a full disclosure of scientific materials.

“Regulators should stop playing Russian roulette with people’s health,” the group’s spokesperson Franziska Achterberg told the Guardian. “The EU should immediately ban all uses of glyphosate where the chance of people getting in contact with it is high.”

Glyphosate was developed in the 1970s and became the active ingredient in the firm’s $5bn-a-year Roundup brand, as well as Dow’s Accord and Syngenta’s Touchdown.

The weedkiller is so widely-used that residues are commonly found in British bread. One survey found that people in 18 EU countries had traces of the weedkiller in their urine.

Glyphosate-based weedkillers are often mixed with other ‘surfactants’ designed to aid the herbicide’s take-up by plants. Some of these are more toxic than glyphosate itself but manufacturers argue that the product packages should be viewed as secret recipes, as should studies of their toxicity.

Last year, Monsanto reportedly refused to release a toxicity report for Roundup to the Chinese authorities, arguing that it was a trade secret.

According to Andreas Bauer Panskus, the author of a critical report on glyphosate for the TestBiotech research group though, there is a case of glyphosate’s use being restricted.

“I do not think that glyphosate should be banned but its use should be much more restricted,” he said. “While a lot of substances are more toxic than glyphosate, the broad usage of hundreds of thousands of tones of it – particularly on GM crops – is absolutely not a sustainable way to do agriculture or soil use.”

In the UK, the Soil Association has called for a ban on the use of glyphosate by farmers ahead of this year’s harvest. It says use of the weedkiller has risen by 400% in the last 20 years in UK farming and is one of the three pesticides regularly found in routine testing of British bread.

However, bread-makers criticised the NGO for targeting the bread sector and said there was no health risk to consumers.

“There may be a story about Roundup, but not about RoundUp and bread,” said Alex Waugh, director general of the National Association of British & Irish Millers. “It [glyphosate residues] are found in some samples of bread, but the exposure is small. You may want to link them for publicity, but the real story is about glyphosate and the way products are assessed.”
This article was amended on 16 July 2015 to make clear that Efsa would be issuing its opinion on the safety of glyphosate, not on whether or not the license for it should be extended, as the article originally suggested.