IFA President Tim Cullinan said the Glanbia cheese plant in Kilkenny should now proceed without delay after an application by An Taisce to seek leave to apply to the Court of Appeal was turned down.
The project has now been fully considered by Kilkenny County Council, An Bord Pleanála, the High Court and this latest application.
Tim Cullinan said that on each occasion, the process has found in favour of developing the plant at Glanbia's Belview site in Co Kilkenny.
"The decision not to allow a further hearing of An Taisce's objection to the Glanbia cheese plant is the fourth time the project has been upheld," he said.
The Glanbia project was designed as a response to the challenge from Brexit and the need for the farming sector to diversify its products and seek new markets.
"As the most exposed sector in the country, it's reckless of any organisation to obstruct a valid initiative that is designed to safeguard the livelihoods of farm families and the rural economy in the south east," the IFA President said.
An Taisce had said in May that it could not allow the construction of the Glanbia cheese factory in Kilkenny to proceed without a challenge as it will result in the over-intensification of dairy farming, adding that feared the new factory will be a "clear tipping point" for the environment.
The Irish Co-operative Organisation Society also welcomed the decision.
"This decision gives certainty to Glanbia, and to dairy farmers, so that they can plan their businesses, and continue to diversify post Brexit." Long also noted that "the industry has much work to do to support the sustainability of the rural economy, as well as to demonstrate and build on our credentials as producers of high quality, grass-fed sustainable dairy products."
Irish Creamery Milk Suppliers Association President, Pat McCormack, said he hoped the decision of the High Court would be accepted allowing the plant to proceed as soon as possible.
He added that the proposed plant had now been examined in exhausting detail by numerous authorities and experts and all had given permission.
"There's going to be other proposals all across Ireland in the years ahead that will involve the same questions and the same objections," he said.
"We are all – farmers, environmental groups and regulatory bodies – going to have to work out a system where we put forward our analysis based on our best data – and then accept the verdicts of those charged and qualified to make the final decision and do this in a timely manner."