Road casualties in Britain fell last year, although figures show the decline in deaths has now reached a plateau.
There are discrepancies over road accident figures
Deaths fell to 3,201 in 2005, a drop of 0.6%, with serious injuries down 7%.
The Department for Transport released contributory factors for the first time, showing drivers' failure to look properly featured in 32% of accidents.
But in fatal crashes, loss of control was most common, with 35%, and excessive speed was reported in 15% of all accidents and 26% of fatal crashes.
Although the figures for deaths and serious injuries showed a slight fall, the Statistics Commission is concerned police figures, on which government statistics are based, tend to be lower than hospital figures.
If these hospital figures were used, targets would not be met, the commission said. The commission has written to the DfT to express its concern.
The DfT said it was aware of "under-reporting" and that further research will be done. It said it has already produced two reports on the subject.
A spokesman added: "We have always used police figures and they do provide a straight year-on-year comparison."
There was also a fall in the number of drink-drive deaths, with 560 in 2005, a drop of 3%, while total casualties in drink-drive accidents fell by 9%. The figures were based on provisional estimates.
Numbers of cyclist deaths rose 10% to 148, possibly attributable to the rising popularity of commuting by bike. There was a drop in the number of child deaths and serious injuries, with 3,472 occurring in 2005, a drop of 11% on the previous year.
The government has a target to reduce death and serious injury figures by 40% by the year 2010, compared with the average figures between 1994-1998. While there has been a major drop in serious injuries, deaths have remained relatively static.
Andrew Howard, head of road safety for the AA Motoring Trust, said improved car-occupant protection and road design were a major factor in the fall in deaths and serious injuries.
But the RAC Foundation expressed concern over the small decline in road deaths.
Executive director, Edmund King, said: "New thinking is needed to improve driving standards, pedestrian education and poor road and junction design."
The use of contributory factors from police officers' accident reports for the first time have been hailed by campaigners against current policies on speeding.
Safe Speed said the suggestion that speeding or excessive speed for the conditions was a factor in only 15% of accidents showed the "entire road safety policy has been based on dodgy data".
Founder Paul Smith added: "Safe Speed has been pointing out for years that the concentration on speeding was a deadly mistake. Speed cameras must be scrapped. Heads must roll."
But Kevin Clinton, head of road safety at the Royal Society for the Prevention of Accidents, disagreed, saying the report showed a need to re-emphasise the overall campaign against speed.
FATAL CRASH FACTORS
Going too fast for conditions
Failing to look properly
Turning or maneouvring poorly
Exceeding speed limit
The contributory factors suggested eight times more male than female drivers in road accidents were speeding. Older drivers were less likely to speed.
While "impairment or distraction" was reported in 12% of all accidents, and 19% of fatal accidents, a factor like use of a mobile phone did not even feature in 1% of accidents.
Of the six most stated factors, five were some form of mistake by the motorist.
The DfT emphasised that contributory factors were based on the reporting officers initial assessment and were not subjected to a strong standard of proof.