The Association of British Drivers (ABD) has made new claims that cameras have not helped reduce crashes along a stretch of the M4 in Wiltshire.
The ABD paid Wiltshire police for accident statistics and found excessive speed was a factor in 14% of crashes.
Previously the Wiltshire and Swindon Safety Camera Partnership (WSSCP) said cameras had reduced crashes by 64%.
Paul Smith, of the independent Safe Speed campaign said the WSSCP claims did not make sense.
"There is absolutely no mechanism by which their claims could be true," said Mr Smith.
"Far from making the roads safer, cameras have damaged the foundations of British road safety by squandering massive resources on a minor safety factor."
Data supplied to the Department for Transport for the seven specific collision cluster sites on the M4 showed out of the 90 collisions analyzed, 16 (17.77%) were specifically caused by speeding, according to the officer at the scene.
A further 51 were judged to have speed as a causing factor (either inappropriate or excessive speed) and the remaining 23 collisions were not speed related.
Based on this, the WSSCP said: "Therefore out of the 90 collisions examined, 74% were judged to have excess speed or inappropriate speed as a causation factor."
Paul Smith disagrees with the partnership's interpretation of the data.
"Excessive speed is not the same as exceeding a speed limit," he said. "It includes speed inappropriate for the conditions as well as speed in excess of the speed limit."