Farmers have been told to be wary of scam phone calls from brokers and energy companies purporting to be their supplier, pressuring them into signing new contracts.
The NFU said it had received reports from members who had been the target of scam phone calls from energy companies purporting to be NFU Energy.
The union added that these companies had no relation to itself or NFU Energy and should be ignored.
NFU Energy would only ever contact farmers to follow up an email or a planned phone follow up, the NFU said.
"If they know your supplier, supply number and address it may still not be us, this information is publicly available on the electricity database," the NFU explained.
"If you suspect that it isn’t NFU Energy ask us to confirm your unique reference that we hold.
"If you’re unsure of your reference or if they cannot confirm it, the safest thing to do would be to end the call and call us directly on 024 7669 8885.
"We really won’t mind if it was us, as we understand that it’s better to be safe than sorry."
The NFU added: "If they claim to be your supplier but cannot confirm your account number, terminate the call and call back the number on your bill to speak to the supplier directly. Alternatively, call us and we will help as best as we can.
"If you have caller display, look at the number or dial 1471 after the call. NFU Energy call from 024 7669 6512.
"Be very suspicious if it is from a mobile (starting 07) and even more so if it’s unavailable or withheld."
Farmers who have been target of the scam phone calls have been told to help the NFU find out who they are.
Farmers should send copies of anything they receive to email@example.com or post it to NFU Energy, 10th Street, Stoneleigh Park, Kenilworth, CV8 2LS.
"Whatever you do, don’t give any personal information or sign anything if you’re suspicious," the NFU said.
"They will likely try and move you into another contract without your say so with high commissions built-in."