Badger Trust CEO Dominic Dyer told ITV News that Princess Anne is wrong to recommend the gassing of badgers.
"Princess Anne is fundamentally wrong," he said.
"Badger gassing does not work. It is very ineffective because you're pumping gas into a set with lots of tunnel entry and exit points.
"The gas does not disperse equally - it won't kill all the animals outright. On average 20-30% of them will die prolonged, long deaths or suffer brain damage as a consequence.
"So it's not effective and it also has huge humaneness issues associated with it as well."
More top news
Judges will rule if Brexit talks can start without consent from MPs and without formal input from legislatures in Wales, NI and Scotland.
Another cold night across much of England and Wales. Milder conditions pushing into the west of Ireland and Scotland.
US officials have denied that the US military is coordinating with Russia in Syria.