The contractor hired to fell trees at the Glen of the Downs in Co Wicklow as part of a road-widening scheme has expressed concern that some trees have been spiked with nails and other metal objects.
The purpose of spiking the trees was to break chainsaw blades, but it may also result in serious injury to the operators.
Mr Kenneth Davis of the Sawmills, Gorey, Co Wexford, which holds the contract from Wicklow County Council, said a number of objects, including barbed wire and metal, had been affixed to the trees recently.
Mr Davis said he had seen a bicycle tied to a tree, and some trees had barbed wire and bits of metal sticking out of them, which would cause problems.
He said he had not received an anonymous letter of warning which had been delivered to newspapers and the county council yesterday, warning that the action had been taken.
The photocopied, anonymous letter began: "So nice to do this the old-fashioned way!"
It went on to warn: "This is not a hoax. Every tree to be felled in the Glen of the downs has been carefully spiked with 9-inch nails."
The letter said the action was intended as a preventive measure against the "destruction of our natural habitat".
It concluded that those responsible were "in no way affiliated to the attendant protesters" currently camped in the glen.
Mr Davis said half an hour would finish what his workers had to do and they had made no plans to put off the felling, although more care would have to be taken.
A spokesman for Wicklow County Council said it was treating the letter "with the contempt it deserves".
The spokesman said he was aware of the allegations that trees had been spiked, but the council had not yet ascertained the truth or otherwise of the warning.
Ms Kathleen O'Hara, spokeswoman for the group camped in the glen, denied the letter had been sent by anyone associated with the camp or that they had done anything to spike the trees.
"Our policy over the years has been low-impact living, with respect for nature," she added.