Ambulance chiefs have brought in external investigators to probe whether thousands of 999 calls were downgraded, giving paramedics a longer time to respond to emergencies and potentially affecting patients' treatment.

It comes as the head of the East of England Ambulance Service Trust (EEAST) leads the charge to lengthen response times for some emergency calls by reforming targets.

A 'serious incident review' into both the downgrading and upgrading of 999 calls at the trust was due to be published in July. It is now set to be released at the start of January.

The trust declined to comment on the report until it is published, but the EDP understands it centres on an investigation into 999 calls which were reclassified.

Downgrading or upgrading the seriousness of a call changes the target time paramedics have to reach the patient and can potentially affect treatment, as well as the trust's response time performance.

Serious incident reviews are launched when patients die or are harmed in avoidable circumstances or when something happens which could lead to a loss of confidence in the service.

Serious incidents are normally investigated internally with the ambulance service's director of clinical standards reporting to the board about the incident and subsequent probe, but unusually an outside body was brought in to investigate.

At the time the probe began, John Martin was the trust's director of clinical standards but he left this summer for a secondment.

Denise Burke, Labour's Parliamentary Candidate and an Act on Ambulances campaigner, said: 'What we need is more investment in our NHS and the frontline service to bring the improvements required.

'Patients must be told the truth now. We urge anyone who has had a problem with the ambulance service to speak out.'

Ambulances chiefs are pushing at the moment for response time targets to change to give crews 19 minutes rather than the current eight minutes to attend some serious, but not the most life-threatening, calls, known as 'Red 2'.

According to a leaked document written for the chief executive of EEAST, Anthony Marsh, 43 per cent of calls currently classed as 'Red 2' will be downgraded.

Some unions and health care minister Norman Lamb have long called for 'Red 2' targets to change, believing it will free up crews to attend the most life-threatening calls.

But Tony Hughes, GMB regional officer for the ambulance service in the East of England, called the proposals 'ridiculous' and warned 'we will see people die'.

The trust is well below hitting the target of arriving at 75% of 'Red 2' calls within eight minutes everywhere in Norfolk apart from Norwich. In North Norfolk, less than 40% of 'Red 2' calls were within the eight minute target in October.

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