Up to 500 lives a year could be saved in London alone if ambulance crews were not slowed down by road humps, researchers say.

The Department for Transport has written to every council in England and Wales, asking them to consult emergency services before installing more humps in response to the research by the London Ambulance Service (LAS).

The LAS has concluded that up to 500 people die in the capital every year if crews responding to emergency calls are delayed by just a minute. The survey showed that a significant number of drivers took detours to avoid humps, and because of jolts caused by them, staff delayed procedures such as inserting intravenous drips.

The department's letter says the research findings "suggest many lives could be saved if vehicles were not restricted by traffic-calming measures''. It adds: "The department acknowledges that full consideration should be given to the wider implications of introducing traffic-calming measures on our roads. This is particularly important with regards to response times for the emergency services.'' Sigurd Reinton, chairman of the LAS, said: "By installing more humps we may prevent more road deaths, but it is possible that we end up paying with many lives lost.''

Barnet council in north London has already begun removing road humps, after deciding that there was no proof that they improved safety. Sixty of the borough's 500 humps have been taken away as roads have been resurfaced.

Brian Coleman, a Barnet councillor, said: "I hope this warning prompts other councils to follow our example.'' He added that many disabled people as well as cyclists had objected to the humps.

Several other London councils, including Enfield, Richmond and Westminster, are changing their policies to make it more difficult for road humps to get planning approval.

But Transport for London (TfL) remains in favour of such traffic-calming measures. It has funded hundreds of humps and says that the average speed on roads with humps falls to 17mph. TfL's research has concluded that 1,400 deaths and serious injuries would be prevented on London's roads every year if a 20mph limit and even more humps were introduced. There are between 20,000 and 30,000 road humps installed in the capital.

A spokesman for LAS said "This is obviously a difficult choice. But we have discovered that in London a delay of a minute means around 500 lives a year. We are not aware of a national figure for this, but obviously there will be some sort of approximation.''

Road humps vary in style, cost and effectiveness. The most expensive, the "speed table", can cost up to £10,000 each. This allows motorists to maintain a reduced but constant speed. The inflatable hump allows a car travelling slowly pass over without disruption. But a car hitting it at speed will bounce.

The "round top", which costs between £ 1,000 and £ 2,000, is considered to be the most damaging to vehicles. The "speed cushion", which consists of Tarmac squares and costs £500, is placed in the middle of each lane, enabling wider axles to straddle them.