The UFU said a notice served on the tractor owner by Antrim and Newtownabbey Council, claims a man was “observed” by an official smoking in a commercial vehicle capable of “carrying more than one person”.
This was deemed to break smoking in the workplace regulations — and the owner, who is also a contractor, was ordered to give the name of the person smoking, or face a fine of up to £1,000.
UFU deputy president Barclay Bell said this seemed to be taking the law to extreme lengths.
The UFU said the incident is a warning to farmers that they cannot escape red tape, even in their tractor, on or off the public road.
A council spokeswoman said investigations are ongoing and no fines or fixed penalties have been issued.
It is against the law to smoke in work vehicles used by more than one person. A tractor is classed as a work vehicle, she said.