Speed bumps and other traffic-calming measures could be costing hundreds of lives a year in London.

The effect of bumps, chicanes and width restrictions on lanes poses a particular risk to heart attack patients, says the London Ambulance Service (LAS).

They estimate every minute added to an emergency journey in London costs up to 500 lives a year.

The LAS has introduced rapid response vehicles to try to overcome the problems posed by increasing traffic calming measures.

Our kids can not go on the roads unless there are those humps slowing traffic down Sir Robin Wales, Association of London Government

But chairman Sigurd Reinton said: "It is the general overall effect of all this traffic calming that slows our vehicles down.

"Even closing rat runs has the effect of forcing the ambulances to go round and make a detour."

Paramedics also find the bumpy ride makes it hard to look after patients in the back of ambulances and even make standing up to reach equipment difficult.

Mr Reinton's comments prompted accusations from the shadow health secretary Dr Liam Fox that "obsession" with traffic calming was "actually killing Londoners".

But Sir Robin Wales, of the Association of London Government, said the ambulance service should look into the impact of traffic calming on children's safety.

He said: "Our kids can not go on the roads unless there are those humps slowing traffic down."