The East of England Ambulance Service has failed an inspection by the health watchdog for its response times in rural areas.
The Care Quality Commission passed the trust on four of the five required standards, but stated that action needs to taken with regards to the care and welfare of people using the service.
A report recognised that response times are being met in areas such as Luton and Peterborough.
However it found that they were not being met in Norfolk and that performance in the county has falled by four per cent since September 2012.
The report states that: “Managers were unable to give us sufficient explanation as to why performance had fallen.”
The Ambulance Service must now send a report by the end of March in which it will set out its plans for improvement.
In a statement, Andrew Morgan, interim Chief Executive of the East of England Ambulance Service said: “I recognise that our performance and response times are simply not good enough.
"That is why we are recruiting more front line staff and seeking to put more ambulances out on the road, whilst also seeking to reduce the delays we experience in handing over patients at hospitals.
"We are also carrying out a clinical capacity review to better understand what resources are required to meet patient demand.
"This is alongside implementing an organisational strategy to better empower, engage and involve staff; together with learning from the good practice of other ambulance services from around the country."
Suffolk Coastal MP, Therese Coffey, has called for management at the trust to consider their positions.
She said: "I strongly believe it's a management problem.
"The government has acted by asking the West Midlands Chief Executive, Anthony Marsh, to go in.
"The trust has already said they don't have enough ambulances or paramedics but my frustration is that none of these issues are new."
We talked to John Martin of the East of England Ambulance Service