A legal battle could be brewing as the European Union fails to agree on granting a new licence for a central weedkiller ingredient glyphosate.

A European Commission proposal to extend the authorisation for glyphosate – found in agricultural product such as Monsanto's Roundup – for another 12 to 18 months was thrown out by national representatives in the EU's plants, animals, food and feed committee yesterday, until new scientific advice is sought.

There are concerns that the product may be linked to cancer.

The licence runs out at the end of June and if an agreement is not reached, farmers will no longer by able to us anything containing glysophate, which is the most used herbicide in the world, by December 2018

Speaking to the Irish Independent, Carlow agronomist warned that it would be a "total disaster" for farming in this country.

He said:

"Glyphosate revolutionised cereal production here since it became available in the 1970s. It has increased cereal yields and reduced costs by controlling scutch.

"There is no other herbicide out there that will control scutch roots.

"A graminicide will control it temporarily, but there would be very limited options for its use in cereal crops."

Despite the World Health Organisation's (WHO) cancer agency concluding last year that the product was "probably carcinogenic" to humans, a May report from WHO and the United Nation's Food and Agricultural Organization concluded that it was "unlikely to pose a carcinogenic risk" through diet.

The US-based Monsanto received a takeover bid of $62bn from Germany's Bayer AG last month and, while Bayer has stated that the EU decision won't affect the deal, if it threatens the future of Monsanto, the matter is likely to end up in the courts.