A US firm pursuing a lawsuit against Monsanto is urging the European Parliament to examine its claims that the agro giant has hidden the dangers of its weedkiller, according to a letter obtained by AFP on Thursday.

The letter from the Los Angeles-based firm comes amid intensifying European Union debate over whether Brussels should renew in December the license for the weedkiller glyphosate for another 10 years.

EU states have been deadlocked for more than a year over whether to declare that the chemical -- used in Monsanto's best-selling herbicide Roundup -- is safe.

The Baum-Hedlund-Aristei-Goldman firm sent a letter dated Wednesday with documents attached which it said bolstered its claims of "corporate malfeasance" by Monsanto.

The letter charged that Monsanto has been "ghostwriting scientific literature designed to make glyphosate look safe, bullying scientists that publish anything negative about their billion-dollar product, and colluding with regulators to ensure 'positive' assessments."

It urged the European Parliament to examine Monsanto's "relationship" with the European Food Safety Authority (EFSA), which ruled earlier this year that glyphosate should not be classified as a carcinogen.

The European Commission, the executive of the 28-nation EU, proposed after the EFSA ruling that the glyphosate license be renewed for 10 years.

The letter also urged the parliament to probe "Monsanto's sponsorship and implementation of ghostwritten scientific literature, specifically designed to influence European authorities."

It asked the Parliament to examine other claims, including Monsanto's alleged "decisions to terminate studies showing much higher asborption rates of glyphosate than previously reported to the EU."

The law firm represents gardeners, farmers, agricultural workers and their families in a lawsuit alleging that Roundup causes cancer.

The weedkiller deadlock in the EU has dragged on since June 2016, when its previous 15-year licence expired.

EU states said then they were unable to make a decision, so the Commission gave a temporary 18-month renewal of glyphosate's licence while more scientific evidence was amassed.

The European Parliament on Tuesday decided to deny access to Monsanto executives and lobbyists after after the firm turned down an invitation to a hearing on October 11 over claims Monsanto influenced scientific research on glyphosate safety.

Monsanto maintains glyphosate "meets or exceeds all requirements for full renewal under European law and regulation" and charged the renewal procedure has in "many respects been hijacked by populism."

source: AFP