The public service workers' union Unison has warned ambulance crews they risk breaking the law by exceeding vehicle weight limits.

Union leaders are raising the prospect of a ban on anyone over 18st 8lbs (260lbs) travelling in an emergency vehicle in the Avon Ambulance Trust area.

They claim each time a crew exceeds the limit in one of the trust's Mercedes 312D vehicles, they are breaking the law and, as such, risk prosecution.

The bid to enforce the strict limits could also mean patients are forced to travel without accompanying relatives while midwives may be banned from travelling with pregnant women.

The trust monitors the weight of its vehicles to ensure that they operate within safety limits.

Terry Hayward

On Monday night, all 300 Avon-based members of Unison were balloted on a motion of no confidence in their management.

Unison officials told crews they had broken the law thousands of times since the 312D range was commissioned in 1994.

Mark Parish, Unison health and safety officer, said: "The onus of responsibility is on the driver.

"If you drive an overladen vehicle and are involved in an incident warranting police investigation, you will be prosecuted, as will the employer."

A spokesman for the Avon Ambulance Service Trust said a vehicle, fully-laden with staff and equipment still left "sufficient leeway".

'Safety limits'

Karen Higginson, of the trust said: "Mark Parish wrote to us expressing his concerns and sent a copy of that letter to the Western Daily Press and the Bristol Evening Post, before he had given us a chance to respond."

Terry Hayward, Director of Operations at the trust said: "The figures Mr Parrish quotes are wrong.

"The trust monitors the weight of its vehicles to ensure that they operate within safety limits.

"The day we received Mr Parrish's letter one of the vehicles in question was weighed, fully laden, with staff, on a licensed weighbridge, and it was well within safety limits."