THE problem that led to a £4m fleet of ambulances being mothballed could have been avoided before it even arose, it was claimed today.

If 999 crews had been consulted at the design stage the flaw would have been spotted and dealt with before the first vehicles were delivered, according to the union Unison.

But instead they were frozen out of the process and the 40-strong fleet of supposedly state-of-the-art vehicles have been mothballed since soon after they were delivered.

The Mercedes ambulances were bought by the Tees, East and North Yorkshire Ambulance Service (Tenyas) last year to replace ageing vehicles with high mileages.

But shortly after the first batch arrived from Germany a fundamental problem became clear - they could not cope with traffic-calming speed bumps.

The difficulty was caused by the weight of the hydraulic lifts fitted to the back of the ambulances in order to get wheelchairs in and out of them easily.

However the lifts apparently make the vehicles sit lower down on the road than they would otherwise.

And as a result the ambulances "bottom out" and strike the road surface when driven over the traffic-calming bumps.

Crews are now having to continue using the older vehicles while the modern fleet remains parked up at various ambulance stations, awaiting modifications which bosses claim should be completed by the end of September.

Unison area secretary Glen Gears, a paramedic based at York, said today: "We were not invited to join the regional vehicle group that was set up a couple of years ago so we had no input into the design stage.

"In the past staff have been involved in discussions but this time it was felt to be unnecessary for some reason."

He added: "This could certainly have been avoided if we were involved at the design stage - and when the vehicles first started arriving it was obvious there were going to be some problems.

"The geography of the area, all the hump-back bridges and all the speed bumps were bound to cause bottoming out."

Tenyas's patient services director Tim Lynch said the sophisticated vehicles were the nearest thing to a no-lifting ambulance for crews - given that back injuries are one of the principal reasons for their retirement.

He said a rolling programme of the necessary modifications was now being carried out and would be completed in two months' time.