Most drivers exceed speed limits on clear roads, and two out of three ignore 30mph signs, according to a survey by the Department of Transport.
It found that 56% of car drivers surveyed exceeded 70mph and 19% exceeded 80mph.
On urban roads with a 30mph limit, two-thirds broke the limit, with almost a half of these going faster than 35mph.
The report, Vehicle Speeds in Great Britain: 1999, used data collected at 92 sites for the national traffic census.
On 40mph roads, a quarter of cars exceeded the limit, with 8% exceeding 45 mph. Motorcycles were the vehicles most likely to speed on 40mph urban roads, with 38% breaking the limit. Lorries were also identified as a problem. On urban 30mph roads, 45% of articulated heavy goods vehicles exceeded the limit.
Transport 2000, which accused the government recently of "wimping out" by refusing to impose 20mph limits in 30mph areas, commented yesterday that the survey proved there was a need for stronger enforcement by police and awareness from motorists that speeding was as unacceptable as drink-driving.
The group pointed out that 5,000 non-drivers - children, pedestrians and cyclists - were killed each year. "The first priority has to be to get drivers to realise they must not break the limit and that, if they do, they will be stopped and fined," said spokesman Steve Hounsham. "That 67% of drivers deliberately ignore limits is totally unacceptable. That's why we have such huge carnage on Britain's roads."
The RAC said the survey suggested there was a need to rethink speed limits. "I think 80mph would be a more reasonable limit for motorways, given that modern cars are much safer," said spokesman Jonathan Simpson. "In terms of urban roads, there's an argument for looking at limits more intelligently rather than just blanket speed reductions. Perhaps we could have 20mph limits around areas where there are vulnerable people such as schools.
"We need to educate the motorist to respect limits in specific areas, rather than following up knee-jerk reactions from organisations that call for massive crackdowns."
Yesterday, Denise van Outen, 25, pleaded guilty to driving at nearly double the speed limit in her VW Beetle and was warned she faced a driving ban. She admitted the offence by letter, and did not appear before magistrates at Beaconsfield in Buckinghamshire. Sentencing was adjourned for one month for her to appear in person. The former host of Channel 4's Big Breakfast was stopped on the M40 this year on her way to London from her £2m home at Horsenden Manor. Police recorded her doing 73mph past roadworks with a 40mph limit in place.
