Critics of the proposed 80mph speed limits on motorways have accused the Government of "gambling with people's lives" if a trial goes ahead next year.
Reports over the weekend suggested the Government was committed to introducing the higher limit on motorways, and would use roads where variable speed limits are enforced by signs and speed cameras to monitor driving behaviour before rolling it out across other motorways.
But road safety charity Brake has warned that safety will be put at risk if the plan goes ahead.
Julie Townsend, Brake deputy chief executive, said: "This is a gamble with people's lives. There has been no research into the safety of this trial, but there is a mountain of evidence that higher speeds result in more needless and violent crashes and casualties.
"It is hard to see the logic behind this trial when the potential benefits of 80mph limits are so questionable. On our congested motorways they are unlikely to significantly shorten journey times, and could lengthen them by creating an uneven flow and increasing speed differentials between cars and speed-limited trucks. Driving at 80mph also means higher fuel consumption and increased carbon emissions.
"The government should instead look at how it can reduce costly and devastating crashes, and reduce congestion, through more variable speed limits and other measures, without negating the safety benefits by increasing the upper limit. We urge the Transport Secretary to consult road safety groups in the coming weeks to hear their views."
Brake is calling on the government to abandon its plans for 80mph limits on motorways, including this trial, and instead set out how it will deliver benefits to drivers, the wider public and the economy by improving safety and reducing casualties on these roads.
The plan to increase the motorway speed limit was announced in October 2011, with the government suggesting it would help boost the economy by allowing faster journey times.
However, with much of the economy dependent on commercial vehicles which will be restricted to lower speeds, some suggest an 80mph limit would make no difference. But the Government also points to research that half of drivers already exceed the speed limit, it it would merely decriminalise their activity.