Proposals for an 80mph speed limit on the M42 in the Midlands have been branded irresponsible by road safety groups.
The AA wants the higher limit introduced on stretches of motorway where there are variable speed signs, such as the M42 south of Birmingham and the M25 around London.
The motoring group admitted the 80mph limit would need to be vigorously enforced but road safety groups expressed opposition to the plan.
AA Motoring Trust director Bert Morris said: "The current 70mph limit on motorways works well and should not be altered.
"However, on motorways where there are variable speed signs, a limit of 80mph should be introduced when traffic flow and road conditions permit.
"If technology exists to reduce speeds on motorways at certain times, then it ought to be possible to raise speeds when it is suitable to do so.
"However, there will be a need to ensure that drivers do not take the 80mph speed as a signal to do 90mph."
Mary Williams, chief executive of road safety charity Brake, poured scorn on the idea.
She said:"The proposal to raise the limit on motorways is irresponsible and flies in the face of road safety advice and convincing evidence from the USA and elsewhere that raising limits increases casualties.
"The last thing that Government should do is legalise something that is risky just because people are doing it, particularly when there is one death or serious injury on British motorways every seven hours and our motorways are congested and plagued by tired, overstretched drivers who drive too close to each other and lane swap and break the 70mph limit.
"We should be prioritising better enforcement to make our motorways safe."
Rival motoring organisation the RAC echoed Ms Williams' comments, calling for better enforcement of current limits before looking at raising it to 80mph.
A spokesman said: "Simply raising the speed limit isn't going to help safety on the motorways if people's attitudes to speed have not first been changed.
"Clearly, most drivers do not believe the speed limits are enforced or enforceable.
"We believe there should be more police on the motorways rather than relying on cameras."
Overhead gantries have been erected on the stretch of the M42 between the M6 and M40 as part of the Active Traffic Management pilot.
Later this year, ATM will involve downwardly varying speed limits, enforced by speed cameras, and, by the end of next year, using the hard shoulder during periods of congestion.
A Department for Transport spokeswoman said: "There was a review of speed limits carried out a few years ago and it concluded that 70 mph was the right maximum."