The East of England Ambulance Service has been fined £1.2m over failures to reach 75% of life-threatening emergencies within eight minutes.
It has also been fined £300,000 over turnaround times at hospitals. The trust handles more than 900,000 emergency 999 calls a year.
The new fines built up from April to July this year.
The ambulance trust said it was recruiting hundreds of new staff and investing in new ambulances.
The trust must pay the £300,000 fine now and the £1.2m at the end of the financial year.
It serves 19 clinical commissioning groups (CCGs), the GP-led organisations in charge of local NHS budgets.
Wendy Tankard, chief contracts officer at Ipswich and East and West Suffolk Clinical Commissioning Group, said: "We continue to work with the East of England Ambulance Service in transforming the service where it has failed to meet performance standards."
The fines will be distributed among the CCGs according to the percentage of their payment to the ambulance service contract.
The trust recruited a new chief executive in January, Anthony Marsh, who spends three days a week looking after the East of England and two days heading the West Midlands Ambulance Service.
Dr Marsh is on a salary of £232,000. Earlier this week it emerged he had claimed up to £30,000 in hotel and transport expenses over the past 16 months.
"The Commissioning Consortium will continue to work with and monitor the East of England Ambulance Service Trust to address areas of underperformance," Ms Tankard said.
The ambulance service said: "We have identified £10m of savings in back office functions and management - money which will be reinvested in more frontline staff.
"We are really pleased with the support from our clinical commissioning groups, especially in the significant investment they have put into the ambulance service this year to enable us to make some of these changes."