A health watchdog warned today that the performance of the ambulance service in Norfolk had deteriorated in the last six months - and said managers had no answers to explain the failings.

A report from the Care Quality Commission (CQC) highlighted the shortcomings of the service stating that response times for emergency calls in Norfolk - categorised as A8 and A19 - had fallen by 4pc since September 2012.

The report said: 'Managers were unable to give us sufficient explanation as to why performance had fallen.'

The CQC passed the ambulance service on four standards, but said improvements were needed in providing care, treatment and support that met people's needs.

It stated: 'People could not be assured they would receive care in a timely and effective manner.'

Inspectors also found that during their time in the ambulance's communications centre a 'high proportion' of ambulances which had been sent out on jobs were either stood down or rerouted to other calls.

Control room staff told the inspectors of an increase in the number of calls to the service which had risen by 9pc in 12 months.

Staff put the worsening response time performance down to a lack of staff to match the increase in calls and handover delays at hospitals.

Suffolk Coastal MP Therese Coffey said: 'It is a sad day for the ambulance trust, as it fails on the key measure of response times with the impact on patients and staff. I am pleased that the good work on other issues has been recognised by CQC. As the first ambulance trust to be failed by CQC on these criteria, Board directors, including the chairman, really do have to ask themselves if this is the right time to continue or if they should step aside.'

'The problems didn't arise overnight and it will take some time to fix but we cannot wait for a year.'

Denise Burke, chair of North Norfolk Labour Party, who led a campaign to improve ambulance response times, described the findings as 'completely unacceptable'.

She said: 'It is unbelievable that over a year since Labour activists raised concerns about response times in north Norfolk with the media that there still appears to have been no further progress at the Trust.

'We also believe that government MPs and health ministers should be held account too for imposing cuts on our ambulance service at a time when it is already struggling. Where is the Secretary of Health, Jeremy Hunt, while this is all happening? He should be taking urgent action.'

•There will be more on this story in tomorrow's Eastern Daily Press.