The national roading authority is felling about 250 rimu, beech, and matai trees from a 70m stretch of the roading corridor beside State Highway 6, between the Haast Pass and Haast.
Transit has cited "untenable" safety risks for travelling motorists posed by the ageing and rotten native trees as the reasons for the felling programme.
However, the Green Party has released obtained photos of the felled native timber, which it claims show the mature rainforest trees are not rotten and dangerous and should never have been removed from a protected World Heritage site.
Green Party Conservation spokeswoman Metiria Turei said the photos showed healthy trees, with normal rot for mature forest giants.
"Some of them may well have graced our highways for centuries or more. The decision to remove them sets an appalling precedent for a national chainsaw massacre," she said.
The "unique trees" would possibly be milled and sold for profit, Ms Turei claimed.
Transit southern zone operations manager Peter Connors said 17 logs, from eight trees out of the 125 which had been felled so far, were taken to a depot in Haast.
Wherever possible, trees were cut so they fell to and remained on the forest floor, he said.
The "salvageable" trees would be milled and the timber sales would probably fetch about $15,000.
Total operational costs of the tree-felling and road corridor clearing came to $180,000, he said.
Mr Connors said the native trees were not part of the protected World Heritage site and were located on the roading corridor under Transit's control.
"Expert advice" predicted there was a strong likelihood that the identified trees would fall over, Mr Connors said.
Department of Conservation South Westland manager Jo Macpherson said the department had no control over the trees felled by Transit.
Doc staff had visited the felling site during the week and had inspected the trees designated for felling.
One beech tree was removed from the felling list after Doc questioned the necessity of cutting down, she said.
Doc had concurred with Transit on the rest of the trees, which posed an unacceptable risk to passing motorists, Ms Macpherson said.
The Otago Conservation Board wrote to Conservation Minister Steve Chadwick yesterday, saying it opposed the felling of healthy, large native trees and asking her to ensure Transit consulted Doc more closely in future.
