The Safe Speed campaign group claims the findings of its research suggest the Government's policy of increasing the number of speed cameras to make roads safer is pointless.
Its research, based on analysis of Department for Transport statistics from 13 police forces, shows the most common cause of accidents is inattention.
This is followed by failure to judge other drivers' path or speed, with excessive speed ranking only seventh. Although alcohol, drugs and tiredness were factors in some accidents, they were not among the top 10 causes.
Campaign founder Paul Smith said: 'When the main causes of accidents involve drivers failing to properly observe or react to road hazards it should be obvious that the modern emphasis on speed limit enforcement by camera risks increasing these common accident types as driver attention is diverted to the speedometer, speed limits and risk of speed enforcement operations.'
Smith added: 'The authorities must now acknowledge that the 'speed kills' road safety policy backed with speed cameras is not benefiting road safety.'
Experts predict the number of speed cameras nationwide will grow to 6,000 units by next spring – up from 4,500 now.
The Government allows police forces to keep a large portion of the revenue raised from fines to fund more cameras.
A spokesman for the Department for Transport said: 'Our research shows speed is a factor in 33% of fatal accidents. This is still a significant number of deaths caused by speed.'