Northern Ireland's largest employer, Moy Park, has said cuts to the Renewable Heat Incentive here have put it at a competitive disadvantage to Great Britain.
In a letter to a Northern Ireland Affairs Committee inquiry, the poultry producer also said the vast majority of its producers were planning to ditch the biomass boilers subsidised by RHI in favour of gas heaters.
Justin Coleman, Moy Park's Agri Business and Live Production Services Director, said there were currently 717 sheds using biomass but by the end of the year over 600 could be using LPG (liquid petroleum gas) boilers, with the rest converting in early 2020.
In April, the average payments for boilers here dropped from around £13,000 to £2,200 a year to become compliant with EU rules on state aid. This compares to average payments of £5,300 in Great Britain.
Moy Park produces half of its chickens in Northern Ireland with the rest in Great Britain. About 80% of chicken produced here is also sold to GB.
Mr Coleman said the difference between the return for the RHI scheme in Northern Ireland and Great Britain had a "discriminatory impact" on local producers.
"Moy Park cannot be reasonably expected to plug the financial gap brought about by changes to the NI RHI Scheme," he said.
"The disparity between NI and GB growers can only be corrected by the UK government."
Ulster Farmers Union deputy president David Brown also wrote to the Inquiry to say RHI cuts in 2019 have placed Northern Ireland "at an immediate competitive disadvantage to all other producers within the UK marketplace".
He said the UFU was still committed to reducing the carbon footprint of the poultry supply chain, but the intense pressure to remain profitable meant members were at a "tipping point" for reverting to fossil fuels.
Mr Brown said the 2019 subsidy cuts had created a "cash-flow shock" for many independent growers, and "corrective action" must be taken immediately to keep them in business.
The short Westminster Inquiry was established to scrutinise the decision to slash RHI payments.
When the flawed green energy scheme was first launched in Northern Ireland, it lacked proper cost controls, with some users making money by burning extra fuel.
The scandal that followed left Stormont with an overspend bill that at one point was predicted to be almost £500m.
When the scale of the problem emerged, new tariffs were enforced to bring the spending under control.
A public inquiry into the fallout, chaired by the retired judge Sir Patrick Coghlin, is set to report later this year.