The NFU, NFU Cymru, NFU Scotland and UFU came together ahead of member state experts voting on a temporary re-extension of authorisation for glyphosate on Monday.
Glyphosate is a herbicide ingredient most commonly known as the main active ingredient in Monsanto's Roundup.
It is almost universally used ahead of reseeding grassland and it is widely used in tillage farming.
If the vote is passed this would be for approximately 18 months until the ECHA (European Union’s Agency for Chemical Products) tables its report next year.
The UK farming unions say there is no "well-reasoned argument" holding back a full re-authorisation of glyphosate in line with the regulatory process.
The letter also states that the glyphosate decision has been subject to "political bargaining".
It begins: "From their fields, yards and orchards across the UK, farmers are following the ongoing debate on the re-approval of glyphosate with mounting concern. To our minds, it comes down to a very simple question: what do we need? What do we need to keep providing people with food, our businesses viable and deliver other public goods that come from farming?"
It goes on to say that European farmers need glyphosate to provide "a safe, secure and affordable food supply" while increasingly responding to consumer demand for greater environmental sensitivity.
"Glyphosate is subject to regulation, as with all other pesticides, so that it is not found in dangerous quantities in the food chain," the presidents write.
"It is also an essential tool used in farming practices that actually improve soil structure and require less work with machinery; thus helping reduce greenhouse gas emissions," they continue.
They also ask that elected officials and policymakers "respect the process" for the re-registration of plant protection products.
IFA grain chair Liam Dunne has previously said that failure to renew the authorisation of glyphosate would deliver "a killer blow" to tillage farming.
”While other users might arguably manage without this active, the removal of glyphosate in the absence of alternative active ingredients to control economically important weeds will deliver a killer blow to the Irish and wider EU tillage sectors,” said Dunne.
Failure to agree
Last month a specialist European Commission committee failed to agree and take a vote on glyphosate licensing renewal because of opposition from several EU member states.
However, Minister for Agriculture Michael Creed recently indicated that Ireland was not one of the member states opposed to the proposal from the Commission, saying it “contained appropriate measures”.
Read the full open letter here.
Stay tuned to farmersjournal.ie for the result of today's vote by EU member states
Full coverage: glyphosate