NFU Cymru is urging farmers to report fly-tipping despite official statistics showing a declining number of cases in Wales on public land.
A report released by NFU Cymru and the NFU found fly-tipping on private had increased by 45%, with clearance costs costing up to £1,200.
The study counted 168 incidents this year, with household waste representing more than half of what is tipped, suggesting a growing trend in opportunistic fly-tipping.
NFU Cymru Meirionnydd county chairman Trefor Hughes said. "It is incredibly unfair that the responsibility for clearing up after those who are flouting the law lies solely with landowners.
"Our main concern is that the Welsh government statistics show that figures are down, but I feel it's quite the opposite; figures are down as farmers simply aren't reporting it. Our message to farmers is if you have been a victim of fly-tipping, report it so that the Welsh government get to see the real picture of how serious this problem is for farmers and landowners."
NFU Cymru would prefer to see a change in legislation to remove the legal responsibility for landowners to deal with fly-tipping on their land.
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