The under pressure East of England ambulance trust is hoping to improve the speed they get to patients by dispatching ambulances that already have a patient on board.
The policy was adopted in August in a bid to improve response times to get to patients with life-threatening injuries or illnesses, known as category one calls.
The trust came bottom of all ambulance trusts in England for category one response times in August.
Commenting on the news, Ms Mayer said: “What a mess. The East of England Ambulance service is on the front line, hemmed in by queues at A&E and attending more call outs because of cuts to social care. This is an NHS crisis made in Downing Street that needs a holistic solution. I’m worried for patients and for hardworking paramedics who are being forced to make impossible choices”