Heavy lorries kill a disproportionate number of cyclists and should be banned from city centres, according to Mark McCarthy and Katy Gilbert of Camden and Islington public health department.

Their study into the deaths of 178 cyclists - aged 3 to 88 - in London from 1985 to 1992 has been published in the British Medical Journal. More than 75 per cent were adults - and 80per cent of them had been hit by a lorry or car. Yet despite the larger number of cars in the capital, heavy lorries were 30 times more likely to kill. There were also fewer fatalities involving buses than lorries.

Project officer Katy Gilbert said: 'The difference could be behavioural, or it may be down to the design of a lorry, which has a huge blind spot and a space underneath. This means cyclists get dragged under the wheels . . . a lot of accidents involve left-hand turning lorries. We believe lorries should be banned on the grounds of health and the environment.

The Government is keen to encourage cycling as it protects people against heart disease and improves fitness. But the report admits many are put off through fear of heavy traffic .

Another study, by Addenbrooke's hospital, Cambridge, looked at 1,000 crash victims and found one-in-ten had serious head injuries. Those wearing helmets were three times less likely to be hurt in that way.