England's motorways aren't safe enough for an 80mph speed limit, according to a report from the Road Safety Foundation (RSF).
The safety charity blames poorly maintained roadside protection and volume of traffic for its findings, which have been published as the Government continues to review the current national speed limit on motorways.
The Government believes that the motorway speed limit could be raised to 80mph to reflect modern motoring. Speaking in autumn 2011, Philip Hammond, the then secretary of state for Transport said that the 'huge economic benefits' of shortening journey times could not be ignored.
However, the RSF says its research has found that widespread faults in run-off protection make it impossible to increase the motorway speed limit to 80mph without risking more death and serious injury.
The RSF says that only a handful of motorway sections, such as the M25 and M40, have electronic controls with hazard warning and variable speed limits that are needed to manage traffic flow across the network.
The RSF's director of road safety, Dr Joanne Marden, said: 'Our cars provide 4-star or 5-star crash protection but too many of our motorways rate only 3-star, with major weakness in run-off protection.
'Large economic benefits arise from fixing the motorways systematically rather than raising the speed limit.'
However, the RSF's report has been slammed as 'seriously flawed' by the Association of British Drivers (ABD).
The ABD's chairman, Brian Gregory, said: 'Motorways are our safest roads by a huge margin, with an accident rate one-seventh that of rural A-roads and one-eleventh that of all rural roads.'
Government plans for speed limits will be revealed later this year and changes will be implemented in early 2013. The review applies to motorways in England and Wales. Responsibilities are devolved in Northern Ireland and are planned to be devolved in Scotland.
Increases in speed limit would apply to cars and motorcycles only.