Proposals to increase the maximum speed limit will cost lives, harm the environment and produce few of the economic benefits claimed by the Government, a report warns.

Ministers are considering raising the speed limit on motorways and dual carriageways from 70 miles per hour to 80mph as part of plans to cut red tape and speed up Britain.

But public health experts, writing in the British Medical Journal, are "amazed" by the idea, which they insist contradicts international road safety evidence. Comparable speed increases introduced in the US in 1995 led to a 16.6 per cent rise in deaths in road accidents.

Martin McKee, professor of European public health at the London School of Hygiene and Tropical Medicine, said there was little evidence to support claims of economic benefits as heavy goods vehicles would still be capped at 60mph. "If the limit moves to 80, most people will drive at 90," he added.

The authors of the report suggested the proposal was nothing more than a "populist gimmick" and wrote: "It is difficult to see how any benefits of an 80mph speed limit would outweigh the costs. Past evidence shows that speed limit increases lead to substantial rises in road deaths, as well as other potential negative health and economic impacts."

Citing the recent crash on the M5 in which seven people lost their lives the authors challenged the Government to provide solid evidence to justify its hopes of pleasing the motoring lobby by raising the limit.

Mike Penning, the Roads minister, said: "[We are] carrying out detailed work to assess the potential impacts of increasing the speed limit and will consult fully on our proposals."