Public transport operator Translink has said it is "sympathetic" to the pressures faced by Northern Ireland farmers and recognised the "important role" they have in the economy and in rural communities after criticism of advertisements on its buses promoting a vegan lifestyle.
The Ulster Farmers Union' (UFU) said its members had raised concerns.
The union said it was felt the ads "wrongly demonise the livestock industry to promote the vegan lifestyle" and members were outraged.
The UFU contacted Translink in an attempt to resolve the dispute but said they were unsatisfied by the response which "reflected an inability to remove them".
Translink said advertising on its vehicles and property was handled by a third party "media specialist" and by carrying the vegan material it was not taking a stance on the issue.
“We are very sympathetic to the pressures facing our local farming community and recognise the important role they have in our economy and rural communities," a spokeswoman said.
One of the adverts reads "it's not a personal choice when someone is killed, use plants not animals", while another says "dairy takes babies from their mothers".
UFU President Ivor Ferguson said the ads were also being printed on the side of school buses.
He said this raised issues in rural areas, with many UFU members relying on Translink's transportation services.
Mr Ferguson described the feelings of the farming community towards the adverts, saying many were "outraged".
"A public service should be impartial on all matters," he said, "but the vegan adverts on the Translink buses use emotive language that singles out our local farmers and has the potential to do serious damage to our agriculture industry and the livelihood of our farming families.
"Our produce is farmed to some of the highest environmental and animal welfare standards in the world so that consumers can enjoy quality food without worrying about what it contains or where it came from but Translink’s adverts dismisses the facts helping to perpetuate a negative narrative about eating meat and consuming dairy products.”
Mr Ferguson outlined the contribution of the farming sector to Northern Ireland "but to demonise the livestock industry to promote another industry is wrong".
"Northern Ireland is the envy of the world when it comes to high-quality food production and animal welfare standards, the agri-food industry turns over £4.5billion annually supporting the Northern Ireland economy and one in every eight jobs in the UK, our farmers care for the environment and many have diversified their businesses helping to boost tourism in local areas, all of which benefits Translink," he said.
The UFU President said in the Republic of Ireland Bus Eireann had removed vegan advertisements "after receiving a high volume of concerns".
"We would like to see Translink do the same," he added.
Go Vegan World, the organisation behind the advertisements, said the ads "merely quote facts about animal use".
The organisation's director, Sandra Higgins, said: “We see this objection to our ads as an indication that people are uncomfortable about earning a living from exploiting defenceless animals and consumers are uncomfortable about creating a demand for the violence of animal agriculture or any other form of animal exploitation.”
"Go Vegan World has always stated that it is not opposed to farmers: it is opposed to their use of other animals as commodities for profit. In fact, Go Vegan World works with farmers to help them transition to a more ethical way of earning a living that is also more sustainable and more environmentally friendly."