The stark warning comes as the government considers increasing the limit from 70mph to 80mph by 2013, with ministers arguing that deaths on roads have fallen by 75 per cent in the past half-century because of advances in car safety.

In addition, some MPs hold that a higher speed limit makes sense as "almost half of all drivers break the current limit anyway."

But a report from the British Medical Journal from the London School of Hygiene and Medicine challenged the government to produce the evidence to justify its policy.

They argued the move would pose other potential negative health risks since a higher limit could increase gas emissions and lead to obesity, with more people taking advantage of shorter car journeys.

Road safety charity Brake believes that the government should work harder to educate drivers on the importance of staying within the existing limit, rather than "pandering to those who are breaking the law.

"Higher speeds equal less time to react and avoid a collision in an emergency," said Brake chief executive Mary Williams.