The number of children under 16 killed on Britain's roads rose by 20% last year, according to figures from the Department for Transport (DfT).
Although traffic has increased, roads are getting safer
But the total number of people killed in road accidents fell slightly over the same period.
In total 3,172 people were killed on the roads in 2006 - a fall on the 3,201 in 2005, despite more traffic.
The number of children under 16 killed rose from 141 to 169 - similar to 2004 suggesting little long term change.
Three years ago 166 youngsters were killed on Britain's roads, said the DfT.
Edmund King, executive director of the RAC Foundation and campaigner for the Make Roads Safe initiative, said: "Children are much more likely to die in a road accident than from drugs or violent crime.
"It's shocking that, in line with global trends, road accidents are the number one killer in the 10-24 age group in the UK."
He said it was essential to educate children about road safety from an early age.
Kevin Clinton, head of road safety at the Royal Society for the Prevention of Accidents (RoSPA), said: "It is appalling that we are seeing more children killed on our roads.
"These figures emphasise a real need to focus on making our roads safer for vulnerable people so that they can walk and cycle without fear."
In general Britain's roads are getting safer - the government has met its target of cutting child deaths by half by 2010, and hopes to cut all deaths and serious injuries by 40% by 2010.
And as provisional figures suggest road traffic levels rose by 1% compared to 2005, it is estimated the overall casualty rate per 100 million vehicle kilometres driven was 6% per cent lower than in 2005.
Car users safer
But road safety experts say too many young teenagers are still being killed, and total pedestrian deaths increased from 671 in 2005 to 675 in 2006.
More motorcyclists were also killed - there were 599 fatalities, a 5% increase from 2005.
But there were less pedal cyclist fatalities, with death rates falling by 1% in 2006.
Car users were also safer in 2006 - the number of deaths was 1,612, 4% down from 2005, and the numbers of car users injured or seriously injured also fell.
A spokesman for the DfT said: "Britain has one of the best road safety records in world.
"Road deaths are now 11% lower than they were in the mid-1990s and they are continuing to fall.
"But any death or injury is one too many and we are working hard to reduce road casualties as far as we can."
But Paul Smith, founder of the anti-speed camera group Safe Speed, said: "The fall of just under 1% in road deaths is further damning evidence of policy failure.
"Most of our European neighbours are achieving falls of 4% or more and we're entitled to at least that.
"Our road safety policies aren't working.
"There's far too much focus on vehicle speeds and no focus at all on driver quality."