Ambulance trusts are warning of financial problems caused by efforts to meet a target for response times to life-threatening emergency calls.
Since 1 April the call connect target has demanded that teams reach 75 per cent of urgent calls within eight minutes of a control centre worker answering the phone.
Great Western Ambulance Service trust blames a£690,000 overspend by the end of June on the change and East of England Ambulance Service trust said it could go£6m over budget.
The West Midlands service said it had spent money on training and "considerable overtime", and in London a£360,000 year to date loss was put down partially to overtime costs to meet performance targets.
Great Western Ambulance Service deputy finance director Simon Truelove said the trust had spent "over and above what primary care trusts have funded", mainly on staff costs.
"The financial position is under control and discussions continue with our commissioners to resolve the current resource issue," he said.
Several trusts have failed to meet the target. In the South East, where the June performance was 70.3 per cent and year to date 69.6 per cent, the chief executive and senior directors are taking part in weekly call connect meetings.
A similar system has been put in place in the East of England, where chief executive Hayden Newton has declared his trust in special measures and is closely managing frontline operations. The trust is seeking additional funds from PCTs.
Ambulance Service Network director Liz Kendall said: "Getting to patients within eight minutes in some rural areas was always going to be a challenge.
"Some are putting on extra services and taking on extra staff to make sure that they can do so."
Though it was "absolutely right" services should get to patients as quickly as possible, she said, attention should also be paid to the quality of care provided.
"Ambulance services are being predominantly focused on call connect whereas, in terms of overall work, that is hugely important but only part of the work they do."
Before 1 April the target was to reach 75 per cent of patients within eight minutes of when details and location had been taken.
A Department of Health spokesman said support and investment had been provided via strategic health authorities and adjustments to capital resource limits to support the changes.
"Ambulance trusts have had time to plan for the introduction of call connect following the launch of the ambulance review in 2005," he said. "Implementation was postponed by ministers until 1 April 2008 to allow trusts to make necessary changes."
HOW TRUSTS SHAPE UP
Calls reached in 8 mins (%)
East of England
Isle of Wight
South East Coast
Figures from July except:
* June figure
**Year to date figure