A proposal to widen a road near the Rollright Stones has been criticised by a conservation charity.
The suggestion was raised at an Oxfordshire County Council meeting discussing the large number of HGVs driving through nearby Chipping Norton.
Transport cabinet member Yvonne Constance said councillor Mike Tysoe's proposal to divert traffic past the ancient site was "doable".
But the chairman of the Rollright Trust said it would "trash" a "key landmark".
Speaking after the meeting, Mr Tysoe said: "Would our Neolithic ancestors mind too much if we save future generations?
"I don't think it will basically damage the site. I've been told it probably won't or there are ways of ensuring that any damage doesn't happen."
George Lambrick, chairman of the Rollright Trust, said such a scheme would be "bonkers".
It would affect the area's tranquillity and cause safety issues for visitors, including schoolchildren, he said.
He added: "Mr Tysoe's flippant remark that 'our Neolithic ancestors would understand' shows he entirely fails to understand, or chooses to ignore, the importance of the Stones nationally, what they mean to people today, or the work of the Rollright Trust looking after them for the benefit of the public."
He said Ms Constance was "shooting from the hip to endorse the idea instead of checking details of heritage and landscape constraints".
Oxfordshire County Council said it was investigating the "most effective ways to improve air quality" in Chipping Norton.
It added: "We have to ensure that any measures we take to remedy matters in Chipping Norton can be funded and actually result in an improvement, and also don't create new problems elsewhere."
The Rollright Stones, which lie within 10m of the road, are believed to have been built over 4,000 years ago, in the Neolithic and Bronze Ages.