Ambulance service bosses have strongly rebutted union claims that major cuts are being planned to the number of front-line staff.

And they denounced the suggestion that staff shortages meant figures were already having to be distorted to meet the government's eight-minute emergency response time, which has to be met in 75pc of cases, as 'untrue, unacceptable and very disappointing'.

A service spokesman was responding yesterday to concerns raised by GMB union organiser Mick Vivian who described the morale of overstretched staff as rock bottom.

He said the situation was made worse by the fact that more than 200 vacancies were not being filled in what staff regarded as a strategy to lose jobs through natural wastage.

'There are also strong rumours going round that after the Olympics 130 ambulances are going to be taken off the road and replaced by 80 cars. The fact that an ambulance has two crew and a car one is an indication of further major job losses,' he said.

Mr Vivian highlighted a case in Essex earlier this month as an example of what he claimed to be the distortion of figures.

A rapid response car had been sent inside eight minutes to an accident victim with a fractured hip. However, all the single paramedic in the vehicle had been able do was make the patient comfortable - on the ground in the rain - until an ambulance arrived two and a half hours later.

The spokesman for the East of England Ambulance Service NHS Trust admitted vacancies were being looked at but insisted there were no plans to make front-line staff redundant.

With regard to the Essex incident cited by Mr Vivian, she said it had not been classed as life-threatening and therefore not subject to the eight-minute deadline to reach patients.

However, she described the long wait for back-up as 'completely unacceptable' and said an investigation was being carried out.