Road casualty figures rose dramatically in the first part of 2014, Government estimates have shown.
There were 380 deaths on British roads in the first three months of this year - 13% more than in the January-March period last year.
Motoring and cycling groups expressed concern at the figures, with the rise only partly explained by the much milder winter following the extreme cold in the first three months of 2013.
Adding the number killed to the number seriously injured, there were 5,500 incidents of KSIs (killed or seriously injured) on the roads in the first quarter of this year - a 17% rise.
Slight injuries also rose, increasing 15% to 40,460. This meant that total casualties - those killed, seriously injured or slightly injured - rose 16% to 45,960.
The statistics for the first three months of 2013 figures include the coldest March in 50 years which could have contributed to the death toll falling to 336.
A more meaningful comparison is the fatality figure for the first three months of 2012 which, at 414, is higher than the estimated figure for January-March 2014.
Also, the fatality figure for the first three months of 2011 was as high as 445.
The latest estimates for January to March 2014 show:
:: Pedestrian KSIs (killed or seriously injured) rose 16% to 1,460;
:: Pedal cyclist KSIs increased 27% to 690, with slight injuries rocketing 43% to 3,830;
:: Motorcyclist KSIs rose 20% to 950;
:: Car user KSIs were up 15% to 2,160;
:: Child (under 16) KSIs increased 17% to 500, with child pedestrian KSIs going up 9% to 350.
Transport Minister Robert Goodwill said: "Britain's roads are among the safest in the world, and the number of deaths last year was the lowest since records began in 1926. Road deaths are down nearly 40% on the average for 2005-2009.
"However, one road death is one too many, which is why we continue to work to tackle dangerous driving and make our roads safer for everyone."
British Cycling's campaigns manager, Martin Key, said: "While cycling is statistically safer than walking, we know that much more could be done to make Britain's roads accommodating for people on bikes. The fact is that our roads are not designed with cycling in mind and these latest road casualty figures are a reflection of that.
"Without adequate and sustained funding for cycling of at least £10 per head, coupled with real political leadership and national targets, Britain will continue to fall far short of great cycling countries like Holland, Germany and Denmark."
RAC technical director David Bizley said: "While the weather must have had an impact on the lower road casualty figures for the first quarter of 2013, the Department for Transport's own recently-released traffic volume data for 2014 only shows a 4.1% year-on-year increase.
"In the absence of a larger difference in traffic volume statistics, which you would, of course, expect if fewer vehicles had been on the road in early 2013, other factors must have contributed to the 16% rise in road casualties.
"It is therefore important that the root cause is understood and acted upon in order to improve road safety for all and reduce the overall number of casualties going forwards."
AA motoring policy head Paul Watters said the January-March 2014 figures were "very disappointing".
He said: "Traffic increases and the weather can be partly to blame and we hope this is no more than a temporary blip to the long-term progress the UK is making in reducing road deaths and injuries."
Rachel Bromley, policy adviser at transport charity Sustrans, said: "Despite Government assurances that our roads are getting safer, these statistics continue to reveal an alarming trend of unnecessary deaths and serious injuries for our most vulnerable roads users.
"The sharp rise in casualties will only serve to further deter people from walking and cycling and promote a growing fear among parents that children are safer inside the car than out.
"It is unacceptable that the Government allows this to continue when a simple solution is at hand. It's time to bite the bullet and make dedicated funding available to transform local walking and cycling routes and introduce lower traffic speeds."